diff --git a/History.md b/History.md
index 478259a02f..8f2c2c2c1d 100644
--- a/History.md
+++ b/History.md
@@ -1,5 +1,14 @@
 ## v.NEXT
 
+* XXX upgraded `less` from 1.3.3 to 1.6.1
+* XXX upgraded `stylus` from 0.37.0 to 0.42.2 and `nib` from `1.0.0` to `1.0.2`
+* XXX sourcemaps support for stylesheets, including less sourcemaps
+* XXX css linting (breaks on errors)
+* XXX css preprocessing to concatenate files correctly (pulls @imports to the
+  beginning)
+* XXX supports `.import.less` and `.import.styl` to prevent Meteor processing
+  stylesheets. `.lessimport` is deprecated
+
 * Hash login tokens before storing them in the database.
 
 * Add `clientAddress` and `httpHeaders` to `this.connection` in method
diff --git a/LICENSE.txt b/LICENSE.txt
index 0f25743305..9897ae8e37 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -71,13 +71,6 @@ handlebars: https://github.com/wycats/handlebars.js/
 Copyright (C) 2011 by Yehuda Katz
 
 
-----------
-clean-css: https://github.com/GoalSmashers/clean-css
-----------
-
-Copyright (c) 2011 GoalSmashers.com
-
-
 ----------
 progress: https://github.com/visionmedia/node-progress
 qs: https://github.com/visionmedia/node-querystring
@@ -91,11 +84,14 @@ pause: https://github.com/visionmedia/node-pause
 range-parser: https://github.com/visionmedia/node-range-parser
 send: https://github.com/visionmedia/send
 methods: https://github.com/visionmedia/node-methods
+css-parse: https://github.com/reworkcss/css-parse
+css-stringify: https://github.com/reworkcss/css-stringify
 ----------
 
 Copyright (c) 2010 TJ Holowaychuk <tj@vision-media.ca>
 Copyright (c) 2011 TJ Holowaychuk <tj@vision-media.ca>
 Copyright (c) 2012 TJ Holowaychuk <tj@vision-media.ca>
+Copyright (c) 2013 TJ Holowaychuk <tj@vision-media.ca>
 
 
 ----------
diff --git a/docs/client/packages/less.html b/docs/client/packages/less.html
index da5145b03d..a4da2ec02f 100644
--- a/docs/client/packages/less.html
+++ b/docs/client/packages/less.html
@@ -11,7 +11,7 @@ automatically compiled to CSS and the results are included in the client CSS
 bundle.
 
 {{#note}}
-If you want to `@import` a file, give it the extension `.lessimport`
+If you want to `@import` a file, give it the extension `.import.less`
 to prevent Meteor from processing it independently.
 {{/note}}
 
diff --git a/docs/client/packages/stylus.html b/docs/client/packages/stylus.html
index 7d3a217028..2752de11a9 100644
--- a/docs/client/packages/stylus.html
+++ b/docs/client/packages/stylus.html
@@ -14,6 +14,11 @@ The `stylus` package also includes `nib` support. Add `@import 'nib'` to
 your `.styl` files to enable cross-browser mixins such as
 `linear-gradient` and `border-radius`.
 
+{{#note}}
+If you want to `@import` a file, give it the extension `.import.styl`
+to prevent Meteor from processing it independently.
+{{/note}}
+
 See <http://visionmedia.github.com/nib> for documentation of the nib extensions of Stylus.
 
 {{/better_markdown}}
diff --git a/meteor b/meteor
index 17a2328b47..ed8d7a22a4 100755
--- a/meteor
+++ b/meteor
@@ -1,9 +1,5 @@
 #!/bin/bash
 
-# danger will robinson!  mother:config/download-dev-bundles.sh only goes up to
-# 0.3.30!
-
-# Before you increment this again, fix the script listed above.
 BUNDLE_VERSION=0.3.30
 
 # OS Check. Put here because here is where we download the precompiled
diff --git a/packages/less/.npm/plugin/compileLess/npm-shrinkwrap.json b/packages/less/.npm/plugin/compileLess/npm-shrinkwrap.json
index 257eeb9951..f2a90d9a9f 100644
--- a/packages/less/.npm/plugin/compileLess/npm-shrinkwrap.json
+++ b/packages/less/.npm/plugin/compileLess/npm-shrinkwrap.json
@@ -1,10 +1,110 @@
 {
   "dependencies": {
     "less": {
-      "version": "1.3.3",
+      "version": "1.6.1",
       "dependencies": {
-        "ycssmin": {
-          "version": "1.0.1"
+        "mime": {
+          "version": "1.2.11"
+        },
+        "request": {
+          "version": "2.33.0",
+          "dependencies": {
+            "qs": {
+              "version": "0.6.6"
+            },
+            "json-stringify-safe": {
+              "version": "5.0.0"
+            },
+            "forever-agent": {
+              "version": "0.5.0"
+            },
+            "node-uuid": {
+              "version": "1.4.1"
+            },
+            "tough-cookie": {
+              "version": "0.12.1",
+              "dependencies": {
+                "punycode": {
+                  "version": "1.2.3"
+                }
+              }
+            },
+            "form-data": {
+              "version": "0.1.2",
+              "dependencies": {
+                "combined-stream": {
+                  "version": "0.0.4",
+                  "dependencies": {
+                    "delayed-stream": {
+                      "version": "0.0.5"
+                    }
+                  }
+                },
+                "async": {
+                  "version": "0.2.10"
+                }
+              }
+            },
+            "tunnel-agent": {
+              "version": "0.3.0"
+            },
+            "http-signature": {
+              "version": "0.10.0",
+              "dependencies": {
+                "assert-plus": {
+                  "version": "0.1.2"
+                },
+                "asn1": {
+                  "version": "0.1.11"
+                },
+                "ctype": {
+                  "version": "0.5.2"
+                }
+              }
+            },
+            "oauth-sign": {
+              "version": "0.3.0"
+            },
+            "hawk": {
+              "version": "1.0.0",
+              "dependencies": {
+                "hoek": {
+                  "version": "0.9.1"
+                },
+                "boom": {
+                  "version": "0.4.2"
+                },
+                "cryptiles": {
+                  "version": "0.2.2"
+                },
+                "sntp": {
+                  "version": "0.2.4"
+                }
+              }
+            },
+            "aws-sign2": {
+              "version": "0.5.0"
+            }
+          }
+        },
+        "mkdirp": {
+          "version": "0.3.5"
+        },
+        "clean-css": {
+          "version": "2.0.7",
+          "dependencies": {
+            "commander": {
+              "version": "2.0.0"
+            }
+          }
+        },
+        "source-map": {
+          "version": "0.1.31",
+          "dependencies": {
+            "amdefine": {
+              "version": "0.1.0"
+            }
+          }
         }
       }
     }
diff --git a/packages/less/less_tests.import.less b/packages/less/less_tests.import.less
new file mode 100644
index 0000000000..f2cbfa1f4c
--- /dev/null
+++ b/packages/less/less_tests.import.less
@@ -0,0 +1,2 @@
+// This should be @import'able into other .less files
+@important-border: double;
diff --git a/packages/less/less_tests.js b/packages/less/less_tests.js
index 262439491c..f64a5b7304 100644
--- a/packages/less/less_tests.js
+++ b/packages/less/less_tests.js
@@ -10,6 +10,7 @@ Tinytest.add("less - presence", function(test) {
 
   // test @import
   test.equal(getStyleProperty(p, 'border-right-style'), "dotted");
+  test.equal(getStyleProperty(p, 'border-bottom-style'), "double");
 
   d.kill();
 });
diff --git a/packages/less/less_tests.less b/packages/less/less_tests.less
index 56e810f570..f97edef951 100644
--- a/packages/less/less_tests.less
+++ b/packages/less/less_tests.less
@@ -1,4 +1,5 @@
 @import "less_tests_constants.lessimport";
+@import "less_tests.import.less";
 
 #less-tests { zoom: 1; /* prop this rule open */ }
 
@@ -7,4 +8,5 @@
 .less-dashy-left-border {
   border-left: @dashy;
   border-right: @external-dotty;
+  border-bottom: @important-border;
 }
diff --git a/packages/less/package.js b/packages/less/package.js
index afe116d38b..4e242a699a 100644
--- a/packages/less/package.js
+++ b/packages/less/package.js
@@ -8,11 +8,12 @@ Package._transitional_registerBuildPlugin({
   sources: [
     'plugin/compile-less.js'
   ],
-  npmDependencies: {"less": "1.3.3"}
+  npmDependencies: {"less": "1.6.1"}
 });
 
 Package.on_test(function (api) {
   api.use(['test-helpers', 'tinytest', 'less']);
   api.use(['spark']);
-  api.add_files(['less_tests.less', 'less_tests.js'], 'client');
+  api.add_files(['less_tests.less', 'less_tests.js', 'less_tests.import.less'],
+                'client');
 });
diff --git a/packages/less/plugin/compile-less.js b/packages/less/plugin/compile-less.js
index 41980738a8..73f24b5206 100644
--- a/packages/less/plugin/compile-less.js
+++ b/packages/less/plugin/compile-less.js
@@ -23,13 +23,14 @@ Plugin.registerSourceHandler("less", function (compileStep) {
     paths: [path.dirname(compileStep._fullInputPath)] // for @import
   };
 
-  var f = new Future;
-  var css;
+  var parser = new less.Parser(options);
+  var astFuture = new Future;
+  var ast;
   try {
-    less.render(source, options, f.resolver());
-    css = f.wait();
+    parser.parse(source, astFuture.resolver());
+    ast = astFuture.wait();
   } catch (e) {
-    // less.render() is supposed to report any errors via its
+    // less.Parser.parse is supposed to report any errors via its
     // callback. But sometimes, it throws them instead. This is
     // probably a bug in less. Be prepared for either behavior.
     compileStep.error({
@@ -41,14 +42,31 @@ Plugin.registerSourceHandler("less", function (compileStep) {
     return;
   }
 
+  var cssFuture = new Future;
+  var css = ast.toCSS({
+    sourceMap: Boolean(true),
+    writeSourceMap: function (sourceMap) {
+      cssFuture.return(sourceMap);
+    }
+  });
+
+  var sourceMap = JSON.parse(cssFuture.wait());
+
+  sourceMap.sources = [compileStep.inputPath];
+  sourceMap.sourcesContent = [source];
+
   compileStep.addStylesheet({
     path: compileStep.inputPath + ".css",
-    data: css
+    data: css,
+    sourceMap: JSON.stringify(sourceMap)
   });
 });;
 
-// Register lessimport files with the dependency watcher, without actually
-// processing them.
-Plugin.registerSourceHandler("lessimport", function () {
+// Register import.less files with the dependency watcher, without actually
+// processing them. There is a similar rule in the stylus package.
+Plugin.registerSourceHandler("import.less", function () {
   // Do nothing
 });
+
+// Backward compatibility with Meteor 0.7
+Plugin.registerSourceHandler("lessimport", function () {});
diff --git a/packages/minifiers/.npm/package/npm-shrinkwrap.json b/packages/minifiers/.npm/package/npm-shrinkwrap.json
index e2eb3b72aa..0b7c29a8b4 100644
--- a/packages/minifiers/.npm/package/npm-shrinkwrap.json
+++ b/packages/minifiers/.npm/package/npm-shrinkwrap.json
@@ -1,13 +1,5 @@
 {
   "dependencies": {
-    "clean-css": {
-      "version": "2.0.2",
-      "dependencies": {
-        "commander": {
-          "version": "2.0.0"
-        }
-      }
-    },
     "uglify-js": {
       "version": "2.4.7",
       "dependencies": {
@@ -34,6 +26,22 @@
           "version": "1.0.1"
         }
       }
+    },
+    "css-parse": {
+      "version": "1.7.0"
+    },
+    "css-stringify": {
+      "version": "1.4.1",
+      "dependencies": {
+        "source-map": {
+          "version": "0.1.31",
+          "dependencies": {
+            "amdefine": {
+              "version": "0.1.0"
+            }
+          }
+        }
+      }
     }
   }
 }
diff --git a/packages/minifiers/minification.js b/packages/minifiers/minification.js
new file mode 100644
index 0000000000..567b8af8c9
--- /dev/null
+++ b/packages/minifiers/minification.js
@@ -0,0 +1,137 @@
+
+// Stringifier based on css-stringify
+var emit = function (str) {
+  return str.toString();
+};
+
+var visit = function (node, last) {
+  return traverse[node.type](node, last);
+};
+
+var mapVisit = function (nodes) {
+  var buf = "";
+
+  for (var i = 0, length = nodes.length; i < length; i++) {
+    buf += visit(nodes[i], i === length - 1);
+  }
+
+  return buf;
+};
+
+MinifyAst = function(node) {
+  return node.stylesheet
+    .rules.map(function (rule) { return visit(rule); })
+    .join('');
+};
+
+var traverse = {};
+
+traverse.comment = function(node) {
+  return emit('', node.position);
+};
+
+traverse.import = function(node) {
+  return emit('@import ' + node.import + ';', node.position);
+};
+
+traverse.media = function(node) {
+  return emit('@media ' + node.media, node.position, true)
+    + emit('{')
+    + mapVisit(node.rules)
+    + emit('}');
+};
+
+traverse.document = function(node) {
+  var doc = '@' + (node.vendor || '') + 'document ' + node.document;
+
+  return emit(doc, node.position, true)
+    + emit('{')
+    + mapVisit(node.rules)
+    + emit('}');
+};
+
+traverse.charset = function(node) {
+  return emit('@charset ' + node.charset + ';', node.position);
+};
+
+traverse.namespace = function(node) {
+  return emit('@namespace ' + node.namespace + ';', node.position);
+};
+
+traverse.supports = function(node){
+  return emit('@supports ' + node.supports, node.position, true)
+    + emit('{')
+    + mapVisit(node.rules)
+    + emit('}');
+};
+
+traverse.keyframes = function(node) {
+  return emit('@'
+    + (node.vendor || '')
+    + 'keyframes '
+    + node.name, node.position, true)
+    + emit('{')
+    + mapVisit(node.keyframes)
+    + emit('}');
+};
+
+traverse.keyframe = function(node) {
+  var decls = node.declarations;
+
+  return emit(node.values.join(','), node.position, true)
+    + emit('{')
+    + mapVisit(decls)
+    + emit('}');
+};
+
+traverse.page = function(node) {
+  var sel = node.selectors.length
+    ? node.selectors.join(', ')
+    : '';
+
+  return emit('@page ' + sel, node.position, true)
+    + emit('{')
+    + mapVisit(node.declarations)
+    + emit('}');
+};
+
+traverse.rule = function(node) {
+  var decls = node.declarations;
+  if (!decls.length) return '';
+
+  var selectors = node.selectors.map(function (selector) {
+    // removes universal selectors like *.class => .class
+    // removes optional whitespace around '>' and '+'
+    return selector.replace(/\*\./, '.')
+                   .replace(/\s*>\s*/g, '>')
+                   .replace(/\s*\+\s*/g, '+');
+  });
+  return emit(selectors.join(','), node.position, true)
+    + emit('{')
+    + mapVisit(decls)
+    + emit('}');
+};
+
+traverse.declaration = function(node, last) {
+  var value = node.value;
+
+  // remove optional quotes around font name
+  if (node.property === 'font') {
+    value = value.replace(/\'[^\']+\'/g, function (m) {
+      if (m.indexOf(' ') !== -1)
+        return m;
+      return m.replace(/\'/g, '');
+    });
+    value = value.replace(/\"[^\"]+\"/g, function (m) {
+      if (m.indexOf(' ') !== -1)
+        return m;
+      return m.replace(/\"/g, '');
+    });
+  }
+  // remove url quotes if possible
+  // in case it is the last declaration, we can omit the semicolon
+  return emit(node.property + ':' + value, node.position)
+         + (last ? '' : emit(';'));
+};
+
+
diff --git a/packages/minifiers/minifiers-tests.js b/packages/minifiers/minifiers-tests.js
new file mode 100644
index 0000000000..282517b430
--- /dev/null
+++ b/packages/minifiers/minifiers-tests.js
@@ -0,0 +1,21 @@
+Tinytest.add("minifiers - simple css minification", function (test) {
+  var t = function (css, expected, desc) {
+    test.equal(CssTools.minifyCss(css), expected, desc);
+  }
+
+  t('a \t\n{ color: red } \n', 'a{color:red}', 'whitespace check');
+  t('a \t\n{ color: red; margin: 1; } \n', 'a{color:red;margin:1}', 'only last one loses semicolon');
+  t('a \t\n{ color: red;;; margin: 1;;; } \n', 'a{color:red;margin:1}', 'more semicolons than needed');
+  t('a , p \t\n{ color: red; } \n', 'a,p{color:red}', 'multiple selectors');
+  t('body {}', '', 'removing empty rules');
+  t('*.my-class { color: #fff; }', '.my-class{color:#fff}', 'removing universal selector');
+  t('p > *.my-class { color: #fff; }', 'p>.my-class{color:#fff}', 'removing optional whitespace around ">" in selector');
+  t('p +  *.my-class { color: #fff; }', 'p+.my-class{color:#fff}', 'removing optional whitespace around "+" in selector');
+  // XXX url parsing is difficult to support at the moment
+  t('a {\n\
+  font:12px \'Helvetica\',"Arial",\'Nautica\';\n\
+  background:url("/some/nice/picture.png");\n}',
+  'a{font:12px Helvetica,Arial,Nautica;background:url("/some/nice/picture.png")}',  'removing quotes in font and url (if possible)');
+  t('/* no comments */ a { color: red; }', 'a{color:red}', 'remove comments');
+});
+
diff --git a/packages/minifiers/minifiers.js b/packages/minifiers/minifiers.js
index ad15487d26..133cf3610c 100644
--- a/packages/minifiers/minifiers.js
+++ b/packages/minifiers/minifiers.js
@@ -1,8 +1,76 @@
-var CleanCss = Npm.require('clean-css');
+UglifyJSMinify = Npm.require('uglify-js').minify;
 
-CleanCSSProcess = function (source, options) {
-  var instance = new CleanCss(options);
-  return instance.minify(source);
+var cssParse = Npm.require('css-parse');
+var cssStringify = Npm.require('css-stringify');
+
+CssTools = {
+  parseCss: cssParse,
+  stringifyCss: cssStringify,
+  minifyCss: function (cssText) {
+    return CssTools.minifyCssAst(cssParse(cssText));
+  },
+  minifyCssAst: function (cssAst) {
+    return MinifyAst(cssAst);
+  },
+  mergeCssAsts: function (cssAsts, warnCb) {
+    var rulesPredicate = function (rules) {
+      if (! _.isArray(rules))
+        rules = [rules];
+      return function (node) {
+        return _.contains(rules, node.type);
+      }
+    };
+
+    // Simple concatenation of CSS files would break @import rules
+    // located in the beginning of a file. Before concatenation, pull them to
+    // the beginning of a new syntax tree so they always precede other rules.
+    var newAst = {
+      type: 'stylesheet',
+      stylesheet: { rules: [] }
+    };
+
+    _.each(cssAsts, function (ast) {
+      // Pick only the imports from the beginning of file ignoring @charset
+      // rules as every file is assumed to be in UTF-8.
+      var charsetRules = _.filter(ast.stylesheet.rules,
+                                  rulesPredicate("charset"));
+
+      if (_.any(charsetRules, function (rule) {
+        // According to MDN, only 'UTF-8' and "UTF-8" are the correct encoding
+        // directives representing UTF-8.
+        return ! /^(['"])UTF-8\1$/.test(rule.charset);
+      })) {
+        warnCb(ast.filename, "@charset rules in this file will be ignored as UTF-8 is the only encoding supported");
+      }
+
+      ast.stylesheet.rules = _.reject(ast.stylesheet.rules,
+                                      rulesPredicate("charset"));
+      var importCount = 0;
+      for (var i = 0; i < ast.stylesheet.rules.length; i++)
+        if (! rulesPredicate(["import", "comment"])(ast.stylesheet.rules[i])) {
+          importCount = i;
+          break;
+        }
+
+      var imports = ast.stylesheet.rules.splice(0, importCount);
+      newAst.stylesheet.rules = newAst.stylesheet.rules.concat(imports);
+
+      // if there are imports left in the middle of file, warn user as it might
+      // be a potential bug (imports are valid only in the beginning of file).
+      if (_.any(ast.stylesheet.rules, rulesPredicate("import"))) {
+        // XXX make this an error?
+        warnCb(ast.filename, "there are some @import rules those are not taking effect as they are required to be in the beginning of the file");
+      }
+
+    });
+
+    // Now we can put the rest of CSS rules into new AST
+    _.each(cssAsts, function (ast) {
+      newAst.stylesheet.rules =
+        newAst.stylesheet.rules.concat(ast.stylesheet.rules);
+    });
+
+    return newAst;
+  }
 };
 
-UglifyJSMinify = Npm.require('uglify-js').minify;
diff --git a/packages/minifiers/package.js b/packages/minifiers/package.js
index c76efd3ee9..70384d6860 100644
--- a/packages/minifiers/package.js
+++ b/packages/minifiers/package.js
@@ -4,11 +4,20 @@ Package.describe({
 });
 
 Npm.depends({
-  "clean-css": "2.0.2",
-  "uglify-js": "2.4.7"
+  "uglify-js": "2.4.7",
+  "css-parse": "1.7.0",
+  "css-stringify": "1.4.1"
 });
 
 Package.on_use(function (api) {
-  api.export(['CleanCSSProcess', 'UglifyJSMinify']);
-  api.add_files('minifiers.js', 'server');
+  api.use('underscore', 'server');
+  api.export(['CssTools', 'UglifyJSMinify']);
+  api.add_files(['minification.js', 'minifiers.js'], 'server');
 });
+
+Package.on_test(function (api) {
+  api.use('minifiers', 'server');
+  api.use('tinytest');
+  api.add_files('minifiers-tests.js', 'server');
+});
+
diff --git a/packages/stylus/.npm/plugin/compileStylus/npm-shrinkwrap.json b/packages/stylus/.npm/plugin/compileStylus/npm-shrinkwrap.json
index a9590cc196..d55ecb4c42 100644
--- a/packages/stylus/.npm/plugin/compileStylus/npm-shrinkwrap.json
+++ b/packages/stylus/.npm/plugin/compileStylus/npm-shrinkwrap.json
@@ -1,27 +1,46 @@
 {
   "dependencies": {
     "stylus": {
-      "version": "0.37.0",
+      "version": "0.42.2",
       "dependencies": {
-        "cssom": {
-          "version": "0.2.5"
+        "css-parse": {
+          "version": "1.7.0"
         },
         "mkdirp": {
           "version": "0.3.5"
         },
         "debug": {
-          "version": "0.7.2"
+          "version": "0.7.4"
         },
         "sax": {
-          "version": "0.5.4"
+          "version": "0.5.8"
+        },
+        "glob": {
+          "version": "3.2.8",
+          "dependencies": {
+            "minimatch": {
+              "version": "0.2.14",
+              "dependencies": {
+                "lru-cache": {
+                  "version": "2.5.0"
+                },
+                "sigmund": {
+                  "version": "1.0.0"
+                }
+              }
+            },
+            "inherits": {
+              "version": "2.0.1"
+            }
+          }
         }
       }
     },
     "nib": {
-      "version": "1.0.0",
+      "version": "1.0.2",
       "dependencies": {
         "stylus": {
-          "version": "0.34.1",
+          "version": "0.37.0",
           "dependencies": {
             "cssom": {
               "version": "0.2.5"
@@ -30,7 +49,10 @@
               "version": "0.3.5"
             },
             "debug": {
-              "version": "0.7.2"
+              "version": "0.7.4"
+            },
+            "sax": {
+              "version": "0.5.8"
             }
           }
         }
diff --git a/packages/stylus/package.js b/packages/stylus/package.js
index 442639ce94..85f04f6552 100644
--- a/packages/stylus/package.js
+++ b/packages/stylus/package.js
@@ -8,11 +8,15 @@ Package._transitional_registerBuildPlugin({
   sources: [
     'plugin/compile-stylus.js'
   ],
-  npmDependencies: { stylus: "0.37.0", nib: "1.0.0" }
+  npmDependencies: { stylus: "0.42.2", nib: "1.0.2" }
 });
 
 Package.on_test(function (api) {
   api.use(['tinytest', 'stylus', 'test-helpers']);
   api.use('spark');
-  api.add_files(['stylus_tests.styl', 'stylus_tests.js'], 'client');
+  api.add_files([
+    'stylus_tests.styl',
+    'stylus_tests.import.styl',
+    'stylus_tests.js'
+  ],'client');
 });
diff --git a/packages/stylus/plugin/compile-stylus.js b/packages/stylus/plugin/compile-stylus.js
index 7ddc33dcf5..7e3c7372e5 100644
--- a/packages/stylus/plugin/compile-stylus.js
+++ b/packages/stylus/plugin/compile-stylus.js
@@ -1,6 +1,7 @@
 var fs = Npm.require('fs');
 var stylus = Npm.require('stylus');
 var nib = Npm.require('nib');
+var path = Npm.require('path');
 var Future = Npm.require('fibers/future');
 
 Plugin.registerSourceHandler("styl", function (compileStep) {
@@ -17,6 +18,8 @@ Plugin.registerSourceHandler("styl", function (compileStep) {
   stylus(compileStep.read().toString('utf8'))
     .use(nib())
     .set('filename', compileStep.inputPath)
+    // Include needed to allow relative @imports in stylus files
+    .include(path.dirname(compileStep._fullInputPath))
     .render(f.resolver());
 
   try {
@@ -32,3 +35,10 @@ Plugin.registerSourceHandler("styl", function (compileStep) {
     data: css
   });
 });
+
+// Register import.styl files with the dependency watcher, without actually
+// processing them. There is a similar rule in the less package.
+Plugin.registerSourceHandler("import.styl", function () {
+  // Do nothing
+});
+
diff --git a/packages/stylus/stylus_tests.import.styl b/packages/stylus/stylus_tests.import.styl
new file mode 100644
index 0000000000..d5e4779860
--- /dev/null
+++ b/packages/stylus/stylus_tests.import.styl
@@ -0,0 +1,5 @@
+// Variable used in stylus_test.styl
+importDashy = dashed
+
+.stylus-overwrite-color
+  font-size: 20px !important
diff --git a/packages/stylus/stylus_tests.js b/packages/stylus/stylus_tests.js
index 0fddbd3420..af8d924a04 100644
--- a/packages/stylus/stylus_tests.js
+++ b/packages/stylus/stylus_tests.js
@@ -1,6 +1,5 @@
 
 Tinytest.add("stylus - presence", function(test) {
-
   var d = OnscreenDiv(Meteor.render(function() {
     return '<p class="stylus-dashy-left-border"></p>'; }));
   d.node().style.display = 'block';
@@ -10,5 +9,17 @@ Tinytest.add("stylus - presence", function(test) {
   test.equal(leftBorder, "dashed");
 
   d.kill();
-
+});
+
+Tinytest.add("stylus - @import", function(test) {
+  var d = OnscreenDiv(Meteor.render(function() {
+    return '<p class="stylus-import-dashy-border stylus-overwrite-color"></p>';
+  }));
+  d.node().style.display = 'block';
+
+  var p = d.node().firstChild;
+  test.equal(getStyleProperty(p, 'font-size'), "20px");
+  test.equal(getStyleProperty(p, 'border-left-style'), "dashed");
+
+  d.kill();
 });
diff --git a/packages/stylus/stylus_tests.styl b/packages/stylus/stylus_tests.styl
index feedadbdf2..46687d5ae2 100644
--- a/packages/stylus/stylus_tests.styl
+++ b/packages/stylus/stylus_tests.styl
@@ -1,3 +1,4 @@
+@import "stylus_tests.import.styl"
 
 #stylus-tests
   zoom: 1
@@ -7,3 +8,9 @@ dashy = dashed
 .stylus-dashy-left-border
   border-left: 1px dashy black
 
+.stylus-overwrite-size
+  // This property is overwritten in stylus_test.import.styl
+  font-size: 10px
+
+.stylus-import-dashy-border
+  border-left: 1px importDashy black
diff --git a/packages/test-in-browser/diff_match_patch_uncompressed.js b/packages/test-in-browser/diff_match_patch_uncompressed.js
new file mode 100644
index 0000000000..112130e097
--- /dev/null
+++ b/packages/test-in-browser/diff_match_patch_uncompressed.js
@@ -0,0 +1,2193 @@
+/**
+ * Diff Match and Patch
+ *
+ * Copyright 2006 Google Inc.
+ * http://code.google.com/p/google-diff-match-patch/
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Computes the difference between two texts to create a patch.
+ * Applies the patch onto another text, allowing for errors.
+ * @author fraser@google.com (Neil Fraser)
+ */
+
+/**
+ * Class containing the diff, match and patch methods.
+ * @constructor
+ */
+function diff_match_patch() {
+
+  // Defaults.
+  // Redefine these in your program to override the defaults.
+
+  // Number of seconds to map a diff before giving up (0 for infinity).
+  this.Diff_Timeout = 1.0;
+  // Cost of an empty edit operation in terms of edit characters.
+  this.Diff_EditCost = 4;
+  // At what point is no match declared (0.0 = perfection, 1.0 = very loose).
+  this.Match_Threshold = 0.5;
+  // How far to search for a match (0 = exact location, 1000+ = broad match).
+  // A match this many characters away from the expected location will add
+  // 1.0 to the score (0.0 is a perfect match).
+  this.Match_Distance = 1000;
+  // When deleting a large block of text (over ~64 characters), how close do
+  // the contents have to be to match the expected contents. (0.0 = perfection,
+  // 1.0 = very loose).  Note that Match_Threshold controls how closely the
+  // end points of a delete need to match.
+  this.Patch_DeleteThreshold = 0.5;
+  // Chunk size for context length.
+  this.Patch_Margin = 4;
+
+  // The number of bits in an int.
+  this.Match_MaxBits = 32;
+}
+
+
+//  DIFF FUNCTIONS
+
+
+/**
+ * The data structure representing a diff is an array of tuples:
+ * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
+ * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
+ */
+var DIFF_DELETE = -1;
+var DIFF_INSERT = 1;
+var DIFF_EQUAL = 0;
+
+/** @typedef {{0: number, 1: string}} */
+diff_match_patch.Diff;
+
+
+/**
+ * Find the differences between two texts.  Simplifies the problem by stripping
+ * any common prefix or suffix off the texts before diffing.
+ * @param {string} text1 Old string to be diffed.
+ * @param {string} text2 New string to be diffed.
+ * @param {boolean=} opt_checklines Optional speedup flag. If present and false,
+ *     then don't run a line-level diff first to identify the changed areas.
+ *     Defaults to true, which does a faster, slightly less optimal diff.
+ * @param {number} opt_deadline Optional time when the diff should be complete
+ *     by.  Used internally for recursive calls.  Users should set DiffTimeout
+ *     instead.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ */
+diff_match_patch.prototype.diff_main = function(text1, text2, opt_checklines,
+    opt_deadline) {
+  // Set a deadline by which time the diff must be complete.
+  if (typeof opt_deadline == 'undefined') {
+    if (this.Diff_Timeout <= 0) {
+      opt_deadline = Number.MAX_VALUE;
+    } else {
+      opt_deadline = (new Date).getTime() + this.Diff_Timeout * 1000;
+    }
+  }
+  var deadline = opt_deadline;
+
+  // Check for null inputs.
+  if (text1 == null || text2 == null) {
+    throw new Error('Null input. (diff_main)');
+  }
+
+  // Check for equality (speedup).
+  if (text1 == text2) {
+    if (text1) {
+      return [[DIFF_EQUAL, text1]];
+    }
+    return [];
+  }
+
+  if (typeof opt_checklines == 'undefined') {
+    opt_checklines = true;
+  }
+  var checklines = opt_checklines;
+
+  // Trim off common prefix (speedup).
+  var commonlength = this.diff_commonPrefix(text1, text2);
+  var commonprefix = text1.substring(0, commonlength);
+  text1 = text1.substring(commonlength);
+  text2 = text2.substring(commonlength);
+
+  // Trim off common suffix (speedup).
+  commonlength = this.diff_commonSuffix(text1, text2);
+  var commonsuffix = text1.substring(text1.length - commonlength);
+  text1 = text1.substring(0, text1.length - commonlength);
+  text2 = text2.substring(0, text2.length - commonlength);
+
+  // Compute the diff on the middle block.
+  var diffs = this.diff_compute_(text1, text2, checklines, deadline);
+
+  // Restore the prefix and suffix.
+  if (commonprefix) {
+    diffs.unshift([DIFF_EQUAL, commonprefix]);
+  }
+  if (commonsuffix) {
+    diffs.push([DIFF_EQUAL, commonsuffix]);
+  }
+  this.diff_cleanupMerge(diffs);
+  return diffs;
+};
+
+
+/**
+ * Find the differences between two texts.  Assumes that the texts do not
+ * have any common prefix or suffix.
+ * @param {string} text1 Old string to be diffed.
+ * @param {string} text2 New string to be diffed.
+ * @param {boolean} checklines Speedup flag.  If false, then don't run a
+ *     line-level diff first to identify the changed areas.
+ *     If true, then run a faster, slightly less optimal diff.
+ * @param {number} deadline Time when the diff should be complete by.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ * @private
+ */
+diff_match_patch.prototype.diff_compute_ = function(text1, text2, checklines,
+    deadline) {
+  var diffs;
+
+  if (!text1) {
+    // Just add some text (speedup).
+    return [[DIFF_INSERT, text2]];
+  }
+
+  if (!text2) {
+    // Just delete some text (speedup).
+    return [[DIFF_DELETE, text1]];
+  }
+
+  var longtext = text1.length > text2.length ? text1 : text2;
+  var shorttext = text1.length > text2.length ? text2 : text1;
+  var i = longtext.indexOf(shorttext);
+  if (i != -1) {
+    // Shorter text is inside the longer text (speedup).
+    diffs = [[DIFF_INSERT, longtext.substring(0, i)],
+             [DIFF_EQUAL, shorttext],
+             [DIFF_INSERT, longtext.substring(i + shorttext.length)]];
+    // Swap insertions for deletions if diff is reversed.
+    if (text1.length > text2.length) {
+      diffs[0][0] = diffs[2][0] = DIFF_DELETE;
+    }
+    return diffs;
+  }
+
+  if (shorttext.length == 1) {
+    // Single character string.
+    // After the previous speedup, the character can't be an equality.
+    return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
+  }
+
+  // Check to see if the problem can be split in two.
+  var hm = this.diff_halfMatch_(text1, text2);
+  if (hm) {
+    // A half-match was found, sort out the return data.
+    var text1_a = hm[0];
+    var text1_b = hm[1];
+    var text2_a = hm[2];
+    var text2_b = hm[3];
+    var mid_common = hm[4];
+    // Send both pairs off for separate processing.
+    var diffs_a = this.diff_main(text1_a, text2_a, checklines, deadline);
+    var diffs_b = this.diff_main(text1_b, text2_b, checklines, deadline);
+    // Merge the results.
+    return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b);
+  }
+
+  if (checklines && text1.length > 100 && text2.length > 100) {
+    return this.diff_lineMode_(text1, text2, deadline);
+  }
+
+  return this.diff_bisect_(text1, text2, deadline);
+};
+
+
+/**
+ * Do a quick line-level diff on both strings, then rediff the parts for
+ * greater accuracy.
+ * This speedup can produce non-minimal diffs.
+ * @param {string} text1 Old string to be diffed.
+ * @param {string} text2 New string to be diffed.
+ * @param {number} deadline Time when the diff should be complete by.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ * @private
+ */
+diff_match_patch.prototype.diff_lineMode_ = function(text1, text2, deadline) {
+  // Scan the text on a line-by-line basis first.
+  var a = this.diff_linesToChars_(text1, text2);
+  text1 = a.chars1;
+  text2 = a.chars2;
+  var linearray = a.lineArray;
+
+  var diffs = this.diff_main(text1, text2, false, deadline);
+
+  // Convert the diff back to original text.
+  this.diff_charsToLines_(diffs, linearray);
+  // Eliminate freak matches (e.g. blank lines)
+  this.diff_cleanupSemantic(diffs);
+
+  // Rediff any replacement blocks, this time character-by-character.
+  // Add a dummy entry at the end.
+  diffs.push([DIFF_EQUAL, '']);
+  var pointer = 0;
+  var count_delete = 0;
+  var count_insert = 0;
+  var text_delete = '';
+  var text_insert = '';
+  while (pointer < diffs.length) {
+    switch (diffs[pointer][0]) {
+      case DIFF_INSERT:
+        count_insert++;
+        text_insert += diffs[pointer][1];
+        break;
+      case DIFF_DELETE:
+        count_delete++;
+        text_delete += diffs[pointer][1];
+        break;
+      case DIFF_EQUAL:
+        // Upon reaching an equality, check for prior redundancies.
+        if (count_delete >= 1 && count_insert >= 1) {
+          // Delete the offending records and add the merged ones.
+          diffs.splice(pointer - count_delete - count_insert,
+                       count_delete + count_insert);
+          pointer = pointer - count_delete - count_insert;
+          var a = this.diff_main(text_delete, text_insert, false, deadline);
+          for (var j = a.length - 1; j >= 0; j--) {
+            diffs.splice(pointer, 0, a[j]);
+          }
+          pointer = pointer + a.length;
+        }
+        count_insert = 0;
+        count_delete = 0;
+        text_delete = '';
+        text_insert = '';
+        break;
+    }
+    pointer++;
+  }
+  diffs.pop();  // Remove the dummy entry at the end.
+
+  return diffs;
+};
+
+
+/**
+ * Find the 'middle snake' of a diff, split the problem in two
+ * and return the recursively constructed diff.
+ * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
+ * @param {string} text1 Old string to be diffed.
+ * @param {string} text2 New string to be diffed.
+ * @param {number} deadline Time at which to bail if not yet complete.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ * @private
+ */
+diff_match_patch.prototype.diff_bisect_ = function(text1, text2, deadline) {
+  // Cache the text lengths to prevent multiple calls.
+  var text1_length = text1.length;
+  var text2_length = text2.length;
+  var max_d = Math.ceil((text1_length + text2_length) / 2);
+  var v_offset = max_d;
+  var v_length = 2 * max_d;
+  var v1 = new Array(v_length);
+  var v2 = new Array(v_length);
+  // Setting all elements to -1 is faster in Chrome & Firefox than mixing
+  // integers and undefined.
+  for (var x = 0; x < v_length; x++) {
+    v1[x] = -1;
+    v2[x] = -1;
+  }
+  v1[v_offset + 1] = 0;
+  v2[v_offset + 1] = 0;
+  var delta = text1_length - text2_length;
+  // If the total number of characters is odd, then the front path will collide
+  // with the reverse path.
+  var front = (delta % 2 != 0);
+  // Offsets for start and end of k loop.
+  // Prevents mapping of space beyond the grid.
+  var k1start = 0;
+  var k1end = 0;
+  var k2start = 0;
+  var k2end = 0;
+  for (var d = 0; d < max_d; d++) {
+    // Bail out if deadline is reached.
+    if ((new Date()).getTime() > deadline) {
+      break;
+    }
+
+    // Walk the front path one step.
+    for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
+      var k1_offset = v_offset + k1;
+      var x1;
+      if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
+        x1 = v1[k1_offset + 1];
+      } else {
+        x1 = v1[k1_offset - 1] + 1;
+      }
+      var y1 = x1 - k1;
+      while (x1 < text1_length && y1 < text2_length &&
+             text1.charAt(x1) == text2.charAt(y1)) {
+        x1++;
+        y1++;
+      }
+      v1[k1_offset] = x1;
+      if (x1 > text1_length) {
+        // Ran off the right of the graph.
+        k1end += 2;
+      } else if (y1 > text2_length) {
+        // Ran off the bottom of the graph.
+        k1start += 2;
+      } else if (front) {
+        var k2_offset = v_offset + delta - k1;
+        if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
+          // Mirror x2 onto top-left coordinate system.
+          var x2 = text1_length - v2[k2_offset];
+          if (x1 >= x2) {
+            // Overlap detected.
+            return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
+          }
+        }
+      }
+    }
+
+    // Walk the reverse path one step.
+    for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
+      var k2_offset = v_offset + k2;
+      var x2;
+      if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
+        x2 = v2[k2_offset + 1];
+      } else {
+        x2 = v2[k2_offset - 1] + 1;
+      }
+      var y2 = x2 - k2;
+      while (x2 < text1_length && y2 < text2_length &&
+             text1.charAt(text1_length - x2 - 1) ==
+             text2.charAt(text2_length - y2 - 1)) {
+        x2++;
+        y2++;
+      }
+      v2[k2_offset] = x2;
+      if (x2 > text1_length) {
+        // Ran off the left of the graph.
+        k2end += 2;
+      } else if (y2 > text2_length) {
+        // Ran off the top of the graph.
+        k2start += 2;
+      } else if (!front) {
+        var k1_offset = v_offset + delta - k2;
+        if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
+          var x1 = v1[k1_offset];
+          var y1 = v_offset + x1 - k1_offset;
+          // Mirror x2 onto top-left coordinate system.
+          x2 = text1_length - x2;
+          if (x1 >= x2) {
+            // Overlap detected.
+            return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
+          }
+        }
+      }
+    }
+  }
+  // Diff took too long and hit the deadline or
+  // number of diffs equals number of characters, no commonality at all.
+  return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
+};
+
+
+/**
+ * Given the location of the 'middle snake', split the diff in two parts
+ * and recurse.
+ * @param {string} text1 Old string to be diffed.
+ * @param {string} text2 New string to be diffed.
+ * @param {number} x Index of split point in text1.
+ * @param {number} y Index of split point in text2.
+ * @param {number} deadline Time at which to bail if not yet complete.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ * @private
+ */
+diff_match_patch.prototype.diff_bisectSplit_ = function(text1, text2, x, y,
+    deadline) {
+  var text1a = text1.substring(0, x);
+  var text2a = text2.substring(0, y);
+  var text1b = text1.substring(x);
+  var text2b = text2.substring(y);
+
+  // Compute both diffs serially.
+  var diffs = this.diff_main(text1a, text2a, false, deadline);
+  var diffsb = this.diff_main(text1b, text2b, false, deadline);
+
+  return diffs.concat(diffsb);
+};
+
+
+/**
+ * Split two texts into an array of strings.  Reduce the texts to a string of
+ * hashes where each Unicode character represents one line.
+ * @param {string} text1 First string.
+ * @param {string} text2 Second string.
+ * @return {{chars1: string, chars2: string, lineArray: !Array.<string>}}
+ *     An object containing the encoded text1, the encoded text2 and
+ *     the array of unique strings.
+ *     The zeroth element of the array of unique strings is intentionally blank.
+ * @private
+ */
+diff_match_patch.prototype.diff_linesToChars_ = function(text1, text2) {
+  var lineArray = [];  // e.g. lineArray[4] == 'Hello\n'
+  var lineHash = {};   // e.g. lineHash['Hello\n'] == 4
+
+  // '\x00' is a valid character, but various debuggers don't like it.
+  // So we'll insert a junk entry to avoid generating a null character.
+  lineArray[0] = '';
+
+  /**
+   * Split a text into an array of strings.  Reduce the texts to a string of
+   * hashes where each Unicode character represents one line.
+   * Modifies linearray and linehash through being a closure.
+   * @param {string} text String to encode.
+   * @return {string} Encoded string.
+   * @private
+   */
+  function diff_linesToCharsMunge_(text) {
+    var chars = '';
+    // Walk the text, pulling out a substring for each line.
+    // text.split('\n') would would temporarily double our memory footprint.
+    // Modifying text would create many large strings to garbage collect.
+    var lineStart = 0;
+    var lineEnd = -1;
+    // Keeping our own length variable is faster than looking it up.
+    var lineArrayLength = lineArray.length;
+    while (lineEnd < text.length - 1) {
+      lineEnd = text.indexOf('\n', lineStart);
+      if (lineEnd == -1) {
+        lineEnd = text.length - 1;
+      }
+      var line = text.substring(lineStart, lineEnd + 1);
+      lineStart = lineEnd + 1;
+
+      if (lineHash.hasOwnProperty ? lineHash.hasOwnProperty(line) :
+          (lineHash[line] !== undefined)) {
+        chars += String.fromCharCode(lineHash[line]);
+      } else {
+        chars += String.fromCharCode(lineArrayLength);
+        lineHash[line] = lineArrayLength;
+        lineArray[lineArrayLength++] = line;
+      }
+    }
+    return chars;
+  }
+
+  var chars1 = diff_linesToCharsMunge_(text1);
+  var chars2 = diff_linesToCharsMunge_(text2);
+  return {chars1: chars1, chars2: chars2, lineArray: lineArray};
+};
+
+
+/**
+ * Rehydrate the text in a diff from a string of line hashes to real lines of
+ * text.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @param {!Array.<string>} lineArray Array of unique strings.
+ * @private
+ */
+diff_match_patch.prototype.diff_charsToLines_ = function(diffs, lineArray) {
+  for (var x = 0; x < diffs.length; x++) {
+    var chars = diffs[x][1];
+    var text = [];
+    for (var y = 0; y < chars.length; y++) {
+      text[y] = lineArray[chars.charCodeAt(y)];
+    }
+    diffs[x][1] = text.join('');
+  }
+};
+
+
+/**
+ * Determine the common prefix of two strings.
+ * @param {string} text1 First string.
+ * @param {string} text2 Second string.
+ * @return {number} The number of characters common to the start of each
+ *     string.
+ */
+diff_match_patch.prototype.diff_commonPrefix = function(text1, text2) {
+  // Quick check for common null cases.
+  if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
+    return 0;
+  }
+  // Binary search.
+  // Performance analysis: http://neil.fraser.name/news/2007/10/09/
+  var pointermin = 0;
+  var pointermax = Math.min(text1.length, text2.length);
+  var pointermid = pointermax;
+  var pointerstart = 0;
+  while (pointermin < pointermid) {
+    if (text1.substring(pointerstart, pointermid) ==
+        text2.substring(pointerstart, pointermid)) {
+      pointermin = pointermid;
+      pointerstart = pointermin;
+    } else {
+      pointermax = pointermid;
+    }
+    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
+  }
+  return pointermid;
+};
+
+
+/**
+ * Determine the common suffix of two strings.
+ * @param {string} text1 First string.
+ * @param {string} text2 Second string.
+ * @return {number} The number of characters common to the end of each string.
+ */
+diff_match_patch.prototype.diff_commonSuffix = function(text1, text2) {
+  // Quick check for common null cases.
+  if (!text1 || !text2 ||
+      text1.charAt(text1.length - 1) != text2.charAt(text2.length - 1)) {
+    return 0;
+  }
+  // Binary search.
+  // Performance analysis: http://neil.fraser.name/news/2007/10/09/
+  var pointermin = 0;
+  var pointermax = Math.min(text1.length, text2.length);
+  var pointermid = pointermax;
+  var pointerend = 0;
+  while (pointermin < pointermid) {
+    if (text1.substring(text1.length - pointermid, text1.length - pointerend) ==
+        text2.substring(text2.length - pointermid, text2.length - pointerend)) {
+      pointermin = pointermid;
+      pointerend = pointermin;
+    } else {
+      pointermax = pointermid;
+    }
+    pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
+  }
+  return pointermid;
+};
+
+
+/**
+ * Determine if the suffix of one string is the prefix of another.
+ * @param {string} text1 First string.
+ * @param {string} text2 Second string.
+ * @return {number} The number of characters common to the end of the first
+ *     string and the start of the second string.
+ * @private
+ */
+diff_match_patch.prototype.diff_commonOverlap_ = function(text1, text2) {
+  // Cache the text lengths to prevent multiple calls.
+  var text1_length = text1.length;
+  var text2_length = text2.length;
+  // Eliminate the null case.
+  if (text1_length == 0 || text2_length == 0) {
+    return 0;
+  }
+  // Truncate the longer string.
+  if (text1_length > text2_length) {
+    text1 = text1.substring(text1_length - text2_length);
+  } else if (text1_length < text2_length) {
+    text2 = text2.substring(0, text1_length);
+  }
+  var text_length = Math.min(text1_length, text2_length);
+  // Quick check for the worst case.
+  if (text1 == text2) {
+    return text_length;
+  }
+
+  // Start by looking for a single character match
+  // and increase length until no match is found.
+  // Performance analysis: http://neil.fraser.name/news/2010/11/04/
+  var best = 0;
+  var length = 1;
+  while (true) {
+    var pattern = text1.substring(text_length - length);
+    var found = text2.indexOf(pattern);
+    if (found == -1) {
+      return best;
+    }
+    length += found;
+    if (found == 0 || text1.substring(text_length - length) ==
+        text2.substring(0, length)) {
+      best = length;
+      length++;
+    }
+  }
+};
+
+
+/**
+ * Do the two texts share a substring which is at least half the length of the
+ * longer text?
+ * This speedup can produce non-minimal diffs.
+ * @param {string} text1 First string.
+ * @param {string} text2 Second string.
+ * @return {Array.<string>} Five element Array, containing the prefix of
+ *     text1, the suffix of text1, the prefix of text2, the suffix of
+ *     text2 and the common middle.  Or null if there was no match.
+ * @private
+ */
+diff_match_patch.prototype.diff_halfMatch_ = function(text1, text2) {
+  if (this.Diff_Timeout <= 0) {
+    // Don't risk returning a non-optimal diff if we have unlimited time.
+    return null;
+  }
+  var longtext = text1.length > text2.length ? text1 : text2;
+  var shorttext = text1.length > text2.length ? text2 : text1;
+  if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
+    return null;  // Pointless.
+  }
+  var dmp = this;  // 'this' becomes 'window' in a closure.
+
+  /**
+   * Does a substring of shorttext exist within longtext such that the substring
+   * is at least half the length of longtext?
+   * Closure, but does not reference any external variables.
+   * @param {string} longtext Longer string.
+   * @param {string} shorttext Shorter string.
+   * @param {number} i Start index of quarter length substring within longtext.
+   * @return {Array.<string>} Five element Array, containing the prefix of
+   *     longtext, the suffix of longtext, the prefix of shorttext, the suffix
+   *     of shorttext and the common middle.  Or null if there was no match.
+   * @private
+   */
+  function diff_halfMatchI_(longtext, shorttext, i) {
+    // Start with a 1/4 length substring at position i as a seed.
+    var seed = longtext.substring(i, i + Math.floor(longtext.length / 4));
+    var j = -1;
+    var best_common = '';
+    var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b;
+    while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
+      var prefixLength = dmp.diff_commonPrefix(longtext.substring(i),
+                                               shorttext.substring(j));
+      var suffixLength = dmp.diff_commonSuffix(longtext.substring(0, i),
+                                               shorttext.substring(0, j));
+      if (best_common.length < suffixLength + prefixLength) {
+        best_common = shorttext.substring(j - suffixLength, j) +
+            shorttext.substring(j, j + prefixLength);
+        best_longtext_a = longtext.substring(0, i - suffixLength);
+        best_longtext_b = longtext.substring(i + prefixLength);
+        best_shorttext_a = shorttext.substring(0, j - suffixLength);
+        best_shorttext_b = shorttext.substring(j + prefixLength);
+      }
+    }
+    if (best_common.length * 2 >= longtext.length) {
+      return [best_longtext_a, best_longtext_b,
+              best_shorttext_a, best_shorttext_b, best_common];
+    } else {
+      return null;
+    }
+  }
+
+  // First check if the second quarter is the seed for a half-match.
+  var hm1 = diff_halfMatchI_(longtext, shorttext,
+                             Math.ceil(longtext.length / 4));
+  // Check again based on the third quarter.
+  var hm2 = diff_halfMatchI_(longtext, shorttext,
+                             Math.ceil(longtext.length / 2));
+  var hm;
+  if (!hm1 && !hm2) {
+    return null;
+  } else if (!hm2) {
+    hm = hm1;
+  } else if (!hm1) {
+    hm = hm2;
+  } else {
+    // Both matched.  Select the longest.
+    hm = hm1[4].length > hm2[4].length ? hm1 : hm2;
+  }
+
+  // A half-match was found, sort out the return data.
+  var text1_a, text1_b, text2_a, text2_b;
+  if (text1.length > text2.length) {
+    text1_a = hm[0];
+    text1_b = hm[1];
+    text2_a = hm[2];
+    text2_b = hm[3];
+  } else {
+    text2_a = hm[0];
+    text2_b = hm[1];
+    text1_a = hm[2];
+    text1_b = hm[3];
+  }
+  var mid_common = hm[4];
+  return [text1_a, text1_b, text2_a, text2_b, mid_common];
+};
+
+
+/**
+ * Reduce the number of edits by eliminating semantically trivial equalities.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ */
+diff_match_patch.prototype.diff_cleanupSemantic = function(diffs) {
+  var changes = false;
+  var equalities = [];  // Stack of indices where equalities are found.
+  var equalitiesLength = 0;  // Keeping our own length var is faster in JS.
+  /** @type {?string} */
+  var lastequality = null;
+  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
+  var pointer = 0;  // Index of current position.
+  // Number of characters that changed prior to the equality.
+  var length_insertions1 = 0;
+  var length_deletions1 = 0;
+  // Number of characters that changed after the equality.
+  var length_insertions2 = 0;
+  var length_deletions2 = 0;
+  while (pointer < diffs.length) {
+    if (diffs[pointer][0] == DIFF_EQUAL) {  // Equality found.
+      equalities[equalitiesLength++] = pointer;
+      length_insertions1 = length_insertions2;
+      length_deletions1 = length_deletions2;
+      length_insertions2 = 0;
+      length_deletions2 = 0;
+      lastequality = diffs[pointer][1];
+    } else {  // An insertion or deletion.
+      if (diffs[pointer][0] == DIFF_INSERT) {
+        length_insertions2 += diffs[pointer][1].length;
+      } else {
+        length_deletions2 += diffs[pointer][1].length;
+      }
+      // Eliminate an equality that is smaller or equal to the edits on both
+      // sides of it.
+      if (lastequality && (lastequality.length <=
+          Math.max(length_insertions1, length_deletions1)) &&
+          (lastequality.length <= Math.max(length_insertions2,
+                                           length_deletions2))) {
+        // Duplicate record.
+        diffs.splice(equalities[equalitiesLength - 1], 0,
+                     [DIFF_DELETE, lastequality]);
+        // Change second copy to insert.
+        diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
+        // Throw away the equality we just deleted.
+        equalitiesLength--;
+        // Throw away the previous equality (it needs to be reevaluated).
+        equalitiesLength--;
+        pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1;
+        length_insertions1 = 0;  // Reset the counters.
+        length_deletions1 = 0;
+        length_insertions2 = 0;
+        length_deletions2 = 0;
+        lastequality = null;
+        changes = true;
+      }
+    }
+    pointer++;
+  }
+
+  // Normalize the diff.
+  if (changes) {
+    this.diff_cleanupMerge(diffs);
+  }
+  this.diff_cleanupSemanticLossless(diffs);
+
+  // Find any overlaps between deletions and insertions.
+  // e.g: <del>abcxxx</del><ins>xxxdef</ins>
+  //   -> <del>abc</del>xxx<ins>def</ins>
+  // e.g: <del>xxxabc</del><ins>defxxx</ins>
+  //   -> <ins>def</ins>xxx<del>abc</del>
+  // Only extract an overlap if it is as big as the edit ahead or behind it.
+  pointer = 1;
+  while (pointer < diffs.length) {
+    if (diffs[pointer - 1][0] == DIFF_DELETE &&
+        diffs[pointer][0] == DIFF_INSERT) {
+      var deletion = diffs[pointer - 1][1];
+      var insertion = diffs[pointer][1];
+      var overlap_length1 = this.diff_commonOverlap_(deletion, insertion);
+      var overlap_length2 = this.diff_commonOverlap_(insertion, deletion);
+      if (overlap_length1 >= overlap_length2) {
+        if (overlap_length1 >= deletion.length / 2 ||
+            overlap_length1 >= insertion.length / 2) {
+          // Overlap found.  Insert an equality and trim the surrounding edits.
+          diffs.splice(pointer, 0,
+              [DIFF_EQUAL, insertion.substring(0, overlap_length1)]);
+          diffs[pointer - 1][1] =
+              deletion.substring(0, deletion.length - overlap_length1);
+          diffs[pointer + 1][1] = insertion.substring(overlap_length1);
+          pointer++;
+        }
+      } else {
+        if (overlap_length2 >= deletion.length / 2 ||
+            overlap_length2 >= insertion.length / 2) {
+          // Reverse overlap found.
+          // Insert an equality and swap and trim the surrounding edits.
+          diffs.splice(pointer, 0,
+              [DIFF_EQUAL, deletion.substring(0, overlap_length2)]);
+          diffs[pointer - 1][0] = DIFF_INSERT;
+          diffs[pointer - 1][1] =
+              insertion.substring(0, insertion.length - overlap_length2);
+          diffs[pointer + 1][0] = DIFF_DELETE;
+          diffs[pointer + 1][1] =
+              deletion.substring(overlap_length2);
+          pointer++;
+        }
+      }
+      pointer++;
+    }
+    pointer++;
+  }
+};
+
+
+/**
+ * Look for single edits surrounded on both sides by equalities
+ * which can be shifted sideways to align the edit to a word boundary.
+ * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ */
+diff_match_patch.prototype.diff_cleanupSemanticLossless = function(diffs) {
+  /**
+   * Given two strings, compute a score representing whether the internal
+   * boundary falls on logical boundaries.
+   * Scores range from 6 (best) to 0 (worst).
+   * Closure, but does not reference any external variables.
+   * @param {string} one First string.
+   * @param {string} two Second string.
+   * @return {number} The score.
+   * @private
+   */
+  function diff_cleanupSemanticScore_(one, two) {
+    if (!one || !two) {
+      // Edges are the best.
+      return 6;
+    }
+
+    // Each port of this function behaves slightly differently due to
+    // subtle differences in each language's definition of things like
+    // 'whitespace'.  Since this function's purpose is largely cosmetic,
+    // the choice has been made to use each language's native features
+    // rather than force total conformity.
+    var char1 = one.charAt(one.length - 1);
+    var char2 = two.charAt(0);
+    var nonAlphaNumeric1 = char1.match(diff_match_patch.nonAlphaNumericRegex_);
+    var nonAlphaNumeric2 = char2.match(diff_match_patch.nonAlphaNumericRegex_);
+    var whitespace1 = nonAlphaNumeric1 &&
+        char1.match(diff_match_patch.whitespaceRegex_);
+    var whitespace2 = nonAlphaNumeric2 &&
+        char2.match(diff_match_patch.whitespaceRegex_);
+    var lineBreak1 = whitespace1 &&
+        char1.match(diff_match_patch.linebreakRegex_);
+    var lineBreak2 = whitespace2 &&
+        char2.match(diff_match_patch.linebreakRegex_);
+    var blankLine1 = lineBreak1 &&
+        one.match(diff_match_patch.blanklineEndRegex_);
+    var blankLine2 = lineBreak2 &&
+        two.match(diff_match_patch.blanklineStartRegex_);
+
+    if (blankLine1 || blankLine2) {
+      // Five points for blank lines.
+      return 5;
+    } else if (lineBreak1 || lineBreak2) {
+      // Four points for line breaks.
+      return 4;
+    } else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
+      // Three points for end of sentences.
+      return 3;
+    } else if (whitespace1 || whitespace2) {
+      // Two points for whitespace.
+      return 2;
+    } else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
+      // One point for non-alphanumeric.
+      return 1;
+    }
+    return 0;
+  }
+
+  var pointer = 1;
+  // Intentionally ignore the first and last element (don't need checking).
+  while (pointer < diffs.length - 1) {
+    if (diffs[pointer - 1][0] == DIFF_EQUAL &&
+        diffs[pointer + 1][0] == DIFF_EQUAL) {
+      // This is a single edit surrounded by equalities.
+      var equality1 = diffs[pointer - 1][1];
+      var edit = diffs[pointer][1];
+      var equality2 = diffs[pointer + 1][1];
+
+      // First, shift the edit as far left as possible.
+      var commonOffset = this.diff_commonSuffix(equality1, edit);
+      if (commonOffset) {
+        var commonString = edit.substring(edit.length - commonOffset);
+        equality1 = equality1.substring(0, equality1.length - commonOffset);
+        edit = commonString + edit.substring(0, edit.length - commonOffset);
+        equality2 = commonString + equality2;
+      }
+
+      // Second, step character by character right, looking for the best fit.
+      var bestEquality1 = equality1;
+      var bestEdit = edit;
+      var bestEquality2 = equality2;
+      var bestScore = diff_cleanupSemanticScore_(equality1, edit) +
+          diff_cleanupSemanticScore_(edit, equality2);
+      while (edit.charAt(0) === equality2.charAt(0)) {
+        equality1 += edit.charAt(0);
+        edit = edit.substring(1) + equality2.charAt(0);
+        equality2 = equality2.substring(1);
+        var score = diff_cleanupSemanticScore_(equality1, edit) +
+            diff_cleanupSemanticScore_(edit, equality2);
+        // The >= encourages trailing rather than leading whitespace on edits.
+        if (score >= bestScore) {
+          bestScore = score;
+          bestEquality1 = equality1;
+          bestEdit = edit;
+          bestEquality2 = equality2;
+        }
+      }
+
+      if (diffs[pointer - 1][1] != bestEquality1) {
+        // We have an improvement, save it back to the diff.
+        if (bestEquality1) {
+          diffs[pointer - 1][1] = bestEquality1;
+        } else {
+          diffs.splice(pointer - 1, 1);
+          pointer--;
+        }
+        diffs[pointer][1] = bestEdit;
+        if (bestEquality2) {
+          diffs[pointer + 1][1] = bestEquality2;
+        } else {
+          diffs.splice(pointer + 1, 1);
+          pointer--;
+        }
+      }
+    }
+    pointer++;
+  }
+};
+
+// Define some regex patterns for matching boundaries.
+diff_match_patch.nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/;
+diff_match_patch.whitespaceRegex_ = /\s/;
+diff_match_patch.linebreakRegex_ = /[\r\n]/;
+diff_match_patch.blanklineEndRegex_ = /\n\r?\n$/;
+diff_match_patch.blanklineStartRegex_ = /^\r?\n\r?\n/;
+
+/**
+ * Reduce the number of edits by eliminating operationally trivial equalities.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ */
+diff_match_patch.prototype.diff_cleanupEfficiency = function(diffs) {
+  var changes = false;
+  var equalities = [];  // Stack of indices where equalities are found.
+  var equalitiesLength = 0;  // Keeping our own length var is faster in JS.
+  /** @type {?string} */
+  var lastequality = null;
+  // Always equal to diffs[equalities[equalitiesLength - 1]][1]
+  var pointer = 0;  // Index of current position.
+  // Is there an insertion operation before the last equality.
+  var pre_ins = false;
+  // Is there a deletion operation before the last equality.
+  var pre_del = false;
+  // Is there an insertion operation after the last equality.
+  var post_ins = false;
+  // Is there a deletion operation after the last equality.
+  var post_del = false;
+  while (pointer < diffs.length) {
+    if (diffs[pointer][0] == DIFF_EQUAL) {  // Equality found.
+      if (diffs[pointer][1].length < this.Diff_EditCost &&
+          (post_ins || post_del)) {
+        // Candidate found.
+        equalities[equalitiesLength++] = pointer;
+        pre_ins = post_ins;
+        pre_del = post_del;
+        lastequality = diffs[pointer][1];
+      } else {
+        // Not a candidate, and can never become one.
+        equalitiesLength = 0;
+        lastequality = null;
+      }
+      post_ins = post_del = false;
+    } else {  // An insertion or deletion.
+      if (diffs[pointer][0] == DIFF_DELETE) {
+        post_del = true;
+      } else {
+        post_ins = true;
+      }
+      /*
+       * Five types to be split:
+       * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
+       * <ins>A</ins>X<ins>C</ins><del>D</del>
+       * <ins>A</ins><del>B</del>X<ins>C</ins>
+       * <ins>A</del>X<ins>C</ins><del>D</del>
+       * <ins>A</ins><del>B</del>X<del>C</del>
+       */
+      if (lastequality && ((pre_ins && pre_del && post_ins && post_del) ||
+                           ((lastequality.length < this.Diff_EditCost / 2) &&
+                            (pre_ins + pre_del + post_ins + post_del) == 3))) {
+        // Duplicate record.
+        diffs.splice(equalities[equalitiesLength - 1], 0,
+                     [DIFF_DELETE, lastequality]);
+        // Change second copy to insert.
+        diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
+        equalitiesLength--;  // Throw away the equality we just deleted;
+        lastequality = null;
+        if (pre_ins && pre_del) {
+          // No changes made which could affect previous entry, keep going.
+          post_ins = post_del = true;
+          equalitiesLength = 0;
+        } else {
+          equalitiesLength--;  // Throw away the previous equality.
+          pointer = equalitiesLength > 0 ?
+              equalities[equalitiesLength - 1] : -1;
+          post_ins = post_del = false;
+        }
+        changes = true;
+      }
+    }
+    pointer++;
+  }
+
+  if (changes) {
+    this.diff_cleanupMerge(diffs);
+  }
+};
+
+
+/**
+ * Reorder and merge like edit sections.  Merge equalities.
+ * Any edit section can move as long as it doesn't cross an equality.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ */
+diff_match_patch.prototype.diff_cleanupMerge = function(diffs) {
+  diffs.push([DIFF_EQUAL, '']);  // Add a dummy entry at the end.
+  var pointer = 0;
+  var count_delete = 0;
+  var count_insert = 0;
+  var text_delete = '';
+  var text_insert = '';
+  var commonlength;
+  while (pointer < diffs.length) {
+    switch (diffs[pointer][0]) {
+      case DIFF_INSERT:
+        count_insert++;
+        text_insert += diffs[pointer][1];
+        pointer++;
+        break;
+      case DIFF_DELETE:
+        count_delete++;
+        text_delete += diffs[pointer][1];
+        pointer++;
+        break;
+      case DIFF_EQUAL:
+        // Upon reaching an equality, check for prior redundancies.
+        if (count_delete + count_insert > 1) {
+          if (count_delete !== 0 && count_insert !== 0) {
+            // Factor out any common prefixies.
+            commonlength = this.diff_commonPrefix(text_insert, text_delete);
+            if (commonlength !== 0) {
+              if ((pointer - count_delete - count_insert) > 0 &&
+                  diffs[pointer - count_delete - count_insert - 1][0] ==
+                  DIFF_EQUAL) {
+                diffs[pointer - count_delete - count_insert - 1][1] +=
+                    text_insert.substring(0, commonlength);
+              } else {
+                diffs.splice(0, 0, [DIFF_EQUAL,
+                                    text_insert.substring(0, commonlength)]);
+                pointer++;
+              }
+              text_insert = text_insert.substring(commonlength);
+              text_delete = text_delete.substring(commonlength);
+            }
+            // Factor out any common suffixies.
+            commonlength = this.diff_commonSuffix(text_insert, text_delete);
+            if (commonlength !== 0) {
+              diffs[pointer][1] = text_insert.substring(text_insert.length -
+                  commonlength) + diffs[pointer][1];
+              text_insert = text_insert.substring(0, text_insert.length -
+                  commonlength);
+              text_delete = text_delete.substring(0, text_delete.length -
+                  commonlength);
+            }
+          }
+          // Delete the offending records and add the merged ones.
+          if (count_delete === 0) {
+            diffs.splice(pointer - count_insert,
+                count_delete + count_insert, [DIFF_INSERT, text_insert]);
+          } else if (count_insert === 0) {
+            diffs.splice(pointer - count_delete,
+                count_delete + count_insert, [DIFF_DELETE, text_delete]);
+          } else {
+            diffs.splice(pointer - count_delete - count_insert,
+                count_delete + count_insert, [DIFF_DELETE, text_delete],
+                [DIFF_INSERT, text_insert]);
+          }
+          pointer = pointer - count_delete - count_insert +
+                    (count_delete ? 1 : 0) + (count_insert ? 1 : 0) + 1;
+        } else if (pointer !== 0 && diffs[pointer - 1][0] == DIFF_EQUAL) {
+          // Merge this equality with the previous one.
+          diffs[pointer - 1][1] += diffs[pointer][1];
+          diffs.splice(pointer, 1);
+        } else {
+          pointer++;
+        }
+        count_insert = 0;
+        count_delete = 0;
+        text_delete = '';
+        text_insert = '';
+        break;
+    }
+  }
+  if (diffs[diffs.length - 1][1] === '') {
+    diffs.pop();  // Remove the dummy entry at the end.
+  }
+
+  // Second pass: look for single edits surrounded on both sides by equalities
+  // which can be shifted sideways to eliminate an equality.
+  // e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
+  var changes = false;
+  pointer = 1;
+  // Intentionally ignore the first and last element (don't need checking).
+  while (pointer < diffs.length - 1) {
+    if (diffs[pointer - 1][0] == DIFF_EQUAL &&
+        diffs[pointer + 1][0] == DIFF_EQUAL) {
+      // This is a single edit surrounded by equalities.
+      if (diffs[pointer][1].substring(diffs[pointer][1].length -
+          diffs[pointer - 1][1].length) == diffs[pointer - 1][1]) {
+        // Shift the edit over the previous equality.
+        diffs[pointer][1] = diffs[pointer - 1][1] +
+            diffs[pointer][1].substring(0, diffs[pointer][1].length -
+                                        diffs[pointer - 1][1].length);
+        diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1];
+        diffs.splice(pointer - 1, 1);
+        changes = true;
+      } else if (diffs[pointer][1].substring(0, diffs[pointer + 1][1].length) ==
+          diffs[pointer + 1][1]) {
+        // Shift the edit over the next equality.
+        diffs[pointer - 1][1] += diffs[pointer + 1][1];
+        diffs[pointer][1] =
+            diffs[pointer][1].substring(diffs[pointer + 1][1].length) +
+            diffs[pointer + 1][1];
+        diffs.splice(pointer + 1, 1);
+        changes = true;
+      }
+    }
+    pointer++;
+  }
+  // If shifts were made, the diff needs reordering and another shift sweep.
+  if (changes) {
+    this.diff_cleanupMerge(diffs);
+  }
+};
+
+
+/**
+ * loc is a location in text1, compute and return the equivalent location in
+ * text2.
+ * e.g. 'The cat' vs 'The big cat', 1->1, 5->8
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @param {number} loc Location within text1.
+ * @return {number} Location within text2.
+ */
+diff_match_patch.prototype.diff_xIndex = function(diffs, loc) {
+  var chars1 = 0;
+  var chars2 = 0;
+  var last_chars1 = 0;
+  var last_chars2 = 0;
+  var x;
+  for (x = 0; x < diffs.length; x++) {
+    if (diffs[x][0] !== DIFF_INSERT) {  // Equality or deletion.
+      chars1 += diffs[x][1].length;
+    }
+    if (diffs[x][0] !== DIFF_DELETE) {  // Equality or insertion.
+      chars2 += diffs[x][1].length;
+    }
+    if (chars1 > loc) {  // Overshot the location.
+      break;
+    }
+    last_chars1 = chars1;
+    last_chars2 = chars2;
+  }
+  // Was the location was deleted?
+  if (diffs.length != x && diffs[x][0] === DIFF_DELETE) {
+    return last_chars2;
+  }
+  // Add the remaining character length.
+  return last_chars2 + (loc - last_chars1);
+};
+
+
+/**
+ * Convert a diff array into a pretty HTML report.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @return {string} HTML representation.
+ */
+diff_match_patch.prototype.diff_prettyHtml = function(diffs) {
+  var html = [];
+  var pattern_amp = /&/g;
+  var pattern_lt = /</g;
+  var pattern_gt = />/g;
+  var pattern_para = /\n/g;
+  for (var x = 0; x < diffs.length; x++) {
+    var op = diffs[x][0];    // Operation (insert, delete, equal)
+    var data = diffs[x][1];  // Text of change.
+    var text = data.replace(pattern_amp, '&amp;').replace(pattern_lt, '&lt;')
+        .replace(pattern_gt, '&gt;').replace(pattern_para, '&para;<br>');
+    switch (op) {
+      case DIFF_INSERT:
+        html[x] = '<ins style="background:#e6ffe6;">' + text + '</ins>';
+        break;
+      case DIFF_DELETE:
+        html[x] = '<del style="background:#ffe6e6;">' + text + '</del>';
+        break;
+      case DIFF_EQUAL:
+        html[x] = '<span>' + text + '</span>';
+        break;
+    }
+  }
+  return html.join('');
+};
+
+
+/**
+ * Compute and return the source text (all equalities and deletions).
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @return {string} Source text.
+ */
+diff_match_patch.prototype.diff_text1 = function(diffs) {
+  var text = [];
+  for (var x = 0; x < diffs.length; x++) {
+    if (diffs[x][0] !== DIFF_INSERT) {
+      text[x] = diffs[x][1];
+    }
+  }
+  return text.join('');
+};
+
+
+/**
+ * Compute and return the destination text (all equalities and insertions).
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @return {string} Destination text.
+ */
+diff_match_patch.prototype.diff_text2 = function(diffs) {
+  var text = [];
+  for (var x = 0; x < diffs.length; x++) {
+    if (diffs[x][0] !== DIFF_DELETE) {
+      text[x] = diffs[x][1];
+    }
+  }
+  return text.join('');
+};
+
+
+/**
+ * Compute the Levenshtein distance; the number of inserted, deleted or
+ * substituted characters.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @return {number} Number of changes.
+ */
+diff_match_patch.prototype.diff_levenshtein = function(diffs) {
+  var levenshtein = 0;
+  var insertions = 0;
+  var deletions = 0;
+  for (var x = 0; x < diffs.length; x++) {
+    var op = diffs[x][0];
+    var data = diffs[x][1];
+    switch (op) {
+      case DIFF_INSERT:
+        insertions += data.length;
+        break;
+      case DIFF_DELETE:
+        deletions += data.length;
+        break;
+      case DIFF_EQUAL:
+        // A deletion and an insertion is one substitution.
+        levenshtein += Math.max(insertions, deletions);
+        insertions = 0;
+        deletions = 0;
+        break;
+    }
+  }
+  levenshtein += Math.max(insertions, deletions);
+  return levenshtein;
+};
+
+
+/**
+ * Crush the diff into an encoded string which describes the operations
+ * required to transform text1 into text2.
+ * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
+ * Operations are tab-separated.  Inserted text is escaped using %xx notation.
+ * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
+ * @return {string} Delta text.
+ */
+diff_match_patch.prototype.diff_toDelta = function(diffs) {
+  var text = [];
+  for (var x = 0; x < diffs.length; x++) {
+    switch (diffs[x][0]) {
+      case DIFF_INSERT:
+        text[x] = '+' + encodeURI(diffs[x][1]);
+        break;
+      case DIFF_DELETE:
+        text[x] = '-' + diffs[x][1].length;
+        break;
+      case DIFF_EQUAL:
+        text[x] = '=' + diffs[x][1].length;
+        break;
+    }
+  }
+  return text.join('\t').replace(/%20/g, ' ');
+};
+
+
+/**
+ * Given the original text1, and an encoded string which describes the
+ * operations required to transform text1 into text2, compute the full diff.
+ * @param {string} text1 Source string for the diff.
+ * @param {string} delta Delta text.
+ * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
+ * @throws {!Error} If invalid input.
+ */
+diff_match_patch.prototype.diff_fromDelta = function(text1, delta) {
+  var diffs = [];
+  var diffsLength = 0;  // Keeping our own length var is faster in JS.
+  var pointer = 0;  // Cursor in text1
+  var tokens = delta.split(/\t/g);
+  for (var x = 0; x < tokens.length; x++) {
+    // Each token begins with a one character parameter which specifies the
+    // operation of this token (delete, insert, equality).
+    var param = tokens[x].substring(1);
+    switch (tokens[x].charAt(0)) {
+      case '+':
+        try {
+          diffs[diffsLength++] = [DIFF_INSERT, decodeURI(param)];
+        } catch (ex) {
+          // Malformed URI sequence.
+          throw new Error('Illegal escape in diff_fromDelta: ' + param);
+        }
+        break;
+      case '-':
+        // Fall through.
+      case '=':
+        var n = parseInt(param, 10);
+        if (isNaN(n) || n < 0) {
+          throw new Error('Invalid number in diff_fromDelta: ' + param);
+        }
+        var text = text1.substring(pointer, pointer += n);
+        if (tokens[x].charAt(0) == '=') {
+          diffs[diffsLength++] = [DIFF_EQUAL, text];
+        } else {
+          diffs[diffsLength++] = [DIFF_DELETE, text];
+        }
+        break;
+      default:
+        // Blank tokens are ok (from a trailing \t).
+        // Anything else is an error.
+        if (tokens[x]) {
+          throw new Error('Invalid diff operation in diff_fromDelta: ' +
+                          tokens[x]);
+        }
+    }
+  }
+  if (pointer != text1.length) {
+    throw new Error('Delta length (' + pointer +
+        ') does not equal source text length (' + text1.length + ').');
+  }
+  return diffs;
+};
+
+
+//  MATCH FUNCTIONS
+
+
+/**
+ * Locate the best instance of 'pattern' in 'text' near 'loc'.
+ * @param {string} text The text to search.
+ * @param {string} pattern The pattern to search for.
+ * @param {number} loc The location to search around.
+ * @return {number} Best match index or -1.
+ */
+diff_match_patch.prototype.match_main = function(text, pattern, loc) {
+  // Check for null inputs.
+  if (text == null || pattern == null || loc == null) {
+    throw new Error('Null input. (match_main)');
+  }
+
+  loc = Math.max(0, Math.min(loc, text.length));
+  if (text == pattern) {
+    // Shortcut (potentially not guaranteed by the algorithm)
+    return 0;
+  } else if (!text.length) {
+    // Nothing to match.
+    return -1;
+  } else if (text.substring(loc, loc + pattern.length) == pattern) {
+    // Perfect match at the perfect spot!  (Includes case of null pattern)
+    return loc;
+  } else {
+    // Do a fuzzy compare.
+    return this.match_bitap_(text, pattern, loc);
+  }
+};
+
+
+/**
+ * Locate the best instance of 'pattern' in 'text' near 'loc' using the
+ * Bitap algorithm.
+ * @param {string} text The text to search.
+ * @param {string} pattern The pattern to search for.
+ * @param {number} loc The location to search around.
+ * @return {number} Best match index or -1.
+ * @private
+ */
+diff_match_patch.prototype.match_bitap_ = function(text, pattern, loc) {
+  if (pattern.length > this.Match_MaxBits) {
+    throw new Error('Pattern too long for this browser.');
+  }
+
+  // Initialise the alphabet.
+  var s = this.match_alphabet_(pattern);
+
+  var dmp = this;  // 'this' becomes 'window' in a closure.
+
+  /**
+   * Compute and return the score for a match with e errors and x location.
+   * Accesses loc and pattern through being a closure.
+   * @param {number} e Number of errors in match.
+   * @param {number} x Location of match.
+   * @return {number} Overall score for match (0.0 = good, 1.0 = bad).
+   * @private
+   */
+  function match_bitapScore_(e, x) {
+    var accuracy = e / pattern.length;
+    var proximity = Math.abs(loc - x);
+    if (!dmp.Match_Distance) {
+      // Dodge divide by zero error.
+      return proximity ? 1.0 : accuracy;
+    }
+    return accuracy + (proximity / dmp.Match_Distance);
+  }
+
+  // Highest score beyond which we give up.
+  var score_threshold = this.Match_Threshold;
+  // Is there a nearby exact match? (speedup)
+  var best_loc = text.indexOf(pattern, loc);
+  if (best_loc != -1) {
+    score_threshold = Math.min(match_bitapScore_(0, best_loc), score_threshold);
+    // What about in the other direction? (speedup)
+    best_loc = text.lastIndexOf(pattern, loc + pattern.length);
+    if (best_loc != -1) {
+      score_threshold =
+          Math.min(match_bitapScore_(0, best_loc), score_threshold);
+    }
+  }
+
+  // Initialise the bit arrays.
+  var matchmask = 1 << (pattern.length - 1);
+  best_loc = -1;
+
+  var bin_min, bin_mid;
+  var bin_max = pattern.length + text.length;
+  var last_rd;
+  for (var d = 0; d < pattern.length; d++) {
+    // Scan for the best match; each iteration allows for one more error.
+    // Run a binary search to determine how far from 'loc' we can stray at this
+    // error level.
+    bin_min = 0;
+    bin_mid = bin_max;
+    while (bin_min < bin_mid) {
+      if (match_bitapScore_(d, loc + bin_mid) <= score_threshold) {
+        bin_min = bin_mid;
+      } else {
+        bin_max = bin_mid;
+      }
+      bin_mid = Math.floor((bin_max - bin_min) / 2 + bin_min);
+    }
+    // Use the result from this iteration as the maximum for the next.
+    bin_max = bin_mid;
+    var start = Math.max(1, loc - bin_mid + 1);
+    var finish = Math.min(loc + bin_mid, text.length) + pattern.length;
+
+    var rd = Array(finish + 2);
+    rd[finish + 1] = (1 << d) - 1;
+    for (var j = finish; j >= start; j--) {
+      // The alphabet (s) is a sparse hash, so the following line generates
+      // warnings.
+      var charMatch = s[text.charAt(j - 1)];
+      if (d === 0) {  // First pass: exact match.
+        rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;
+      } else {  // Subsequent passes: fuzzy match.
+        rd[j] = (((rd[j + 1] << 1) | 1) & charMatch) |
+                (((last_rd[j + 1] | last_rd[j]) << 1) | 1) |
+                last_rd[j + 1];
+      }
+      if (rd[j] & matchmask) {
+        var score = match_bitapScore_(d, j - 1);
+        // This match will almost certainly be better than any existing match.
+        // But check anyway.
+        if (score <= score_threshold) {
+          // Told you so.
+          score_threshold = score;
+          best_loc = j - 1;
+          if (best_loc > loc) {
+            // When passing loc, don't exceed our current distance from loc.
+            start = Math.max(1, 2 * loc - best_loc);
+          } else {
+            // Already passed loc, downhill from here on in.
+            break;
+          }
+        }
+      }
+    }
+    // No hope for a (better) match at greater error levels.
+    if (match_bitapScore_(d + 1, loc) > score_threshold) {
+      break;
+    }
+    last_rd = rd;
+  }
+  return best_loc;
+};
+
+
+/**
+ * Initialise the alphabet for the Bitap algorithm.
+ * @param {string} pattern The text to encode.
+ * @return {!Object} Hash of character locations.
+ * @private
+ */
+diff_match_patch.prototype.match_alphabet_ = function(pattern) {
+  var s = {};
+  for (var i = 0; i < pattern.length; i++) {
+    s[pattern.charAt(i)] = 0;
+  }
+  for (var i = 0; i < pattern.length; i++) {
+    s[pattern.charAt(i)] |= 1 << (pattern.length - i - 1);
+  }
+  return s;
+};
+
+
+//  PATCH FUNCTIONS
+
+
+/**
+ * Increase the context until it is unique,
+ * but don't let the pattern expand beyond Match_MaxBits.
+ * @param {!diff_match_patch.patch_obj} patch The patch to grow.
+ * @param {string} text Source text.
+ * @private
+ */
+diff_match_patch.prototype.patch_addContext_ = function(patch, text) {
+  if (text.length == 0) {
+    return;
+  }
+  var pattern = text.substring(patch.start2, patch.start2 + patch.length1);
+  var padding = 0;
+
+  // Look for the first and last matches of pattern in text.  If two different
+  // matches are found, increase the pattern length.
+  while (text.indexOf(pattern) != text.lastIndexOf(pattern) &&
+         pattern.length < this.Match_MaxBits - this.Patch_Margin -
+         this.Patch_Margin) {
+    padding += this.Patch_Margin;
+    pattern = text.substring(patch.start2 - padding,
+                             patch.start2 + patch.length1 + padding);
+  }
+  // Add one chunk for good luck.
+  padding += this.Patch_Margin;
+
+  // Add the prefix.
+  var prefix = text.substring(patch.start2 - padding, patch.start2);
+  if (prefix) {
+    patch.diffs.unshift([DIFF_EQUAL, prefix]);
+  }
+  // Add the suffix.
+  var suffix = text.substring(patch.start2 + patch.length1,
+                              patch.start2 + patch.length1 + padding);
+  if (suffix) {
+    patch.diffs.push([DIFF_EQUAL, suffix]);
+  }
+
+  // Roll back the start points.
+  patch.start1 -= prefix.length;
+  patch.start2 -= prefix.length;
+  // Extend the lengths.
+  patch.length1 += prefix.length + suffix.length;
+  patch.length2 += prefix.length + suffix.length;
+};
+
+
+/**
+ * Compute a list of patches to turn text1 into text2.
+ * Use diffs if provided, otherwise compute it ourselves.
+ * There are four ways to call this function, depending on what data is
+ * available to the caller:
+ * Method 1:
+ * a = text1, b = text2
+ * Method 2:
+ * a = diffs
+ * Method 3 (optimal):
+ * a = text1, b = diffs
+ * Method 4 (deprecated, use method 3):
+ * a = text1, b = text2, c = diffs
+ *
+ * @param {string|!Array.<!diff_match_patch.Diff>} a text1 (methods 1,3,4) or
+ * Array of diff tuples for text1 to text2 (method 2).
+ * @param {string|!Array.<!diff_match_patch.Diff>} opt_b text2 (methods 1,4) or
+ * Array of diff tuples for text1 to text2 (method 3) or undefined (method 2).
+ * @param {string|!Array.<!diff_match_patch.Diff>} opt_c Array of diff tuples
+ * for text1 to text2 (method 4) or undefined (methods 1,2,3).
+ * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
+ */
+diff_match_patch.prototype.patch_make = function(a, opt_b, opt_c) {
+  var text1, diffs;
+  if (typeof a == 'string' && typeof opt_b == 'string' &&
+      typeof opt_c == 'undefined') {
+    // Method 1: text1, text2
+    // Compute diffs from text1 and text2.
+    text1 = /** @type {string} */(a);
+    diffs = this.diff_main(text1, /** @type {string} */(opt_b), true);
+    if (diffs.length > 2) {
+      this.diff_cleanupSemantic(diffs);
+      this.diff_cleanupEfficiency(diffs);
+    }
+  } else if (a && typeof a == 'object' && typeof opt_b == 'undefined' &&
+      typeof opt_c == 'undefined') {
+    // Method 2: diffs
+    // Compute text1 from diffs.
+    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */(a);
+    text1 = this.diff_text1(diffs);
+  } else if (typeof a == 'string' && opt_b && typeof opt_b == 'object' &&
+      typeof opt_c == 'undefined') {
+    // Method 3: text1, diffs
+    text1 = /** @type {string} */(a);
+    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */(opt_b);
+  } else if (typeof a == 'string' && typeof opt_b == 'string' &&
+      opt_c && typeof opt_c == 'object') {
+    // Method 4: text1, text2, diffs
+    // text2 is not used.
+    text1 = /** @type {string} */(a);
+    diffs = /** @type {!Array.<!diff_match_patch.Diff>} */(opt_c);
+  } else {
+    throw new Error('Unknown call format to patch_make.');
+  }
+
+  if (diffs.length === 0) {
+    return [];  // Get rid of the null case.
+  }
+  var patches = [];
+  var patch = new diff_match_patch.patch_obj();
+  var patchDiffLength = 0;  // Keeping our own length var is faster in JS.
+  var char_count1 = 0;  // Number of characters into the text1 string.
+  var char_count2 = 0;  // Number of characters into the text2 string.
+  // Start with text1 (prepatch_text) and apply the diffs until we arrive at
+  // text2 (postpatch_text).  We recreate the patches one by one to determine
+  // context info.
+  var prepatch_text = text1;
+  var postpatch_text = text1;
+  for (var x = 0; x < diffs.length; x++) {
+    var diff_type = diffs[x][0];
+    var diff_text = diffs[x][1];
+
+    if (!patchDiffLength && diff_type !== DIFF_EQUAL) {
+      // A new patch starts here.
+      patch.start1 = char_count1;
+      patch.start2 = char_count2;
+    }
+
+    switch (diff_type) {
+      case DIFF_INSERT:
+        patch.diffs[patchDiffLength++] = diffs[x];
+        patch.length2 += diff_text.length;
+        postpatch_text = postpatch_text.substring(0, char_count2) + diff_text +
+                         postpatch_text.substring(char_count2);
+        break;
+      case DIFF_DELETE:
+        patch.length1 += diff_text.length;
+        patch.diffs[patchDiffLength++] = diffs[x];
+        postpatch_text = postpatch_text.substring(0, char_count2) +
+                         postpatch_text.substring(char_count2 +
+                             diff_text.length);
+        break;
+      case DIFF_EQUAL:
+        if (diff_text.length <= 2 * this.Patch_Margin &&
+            patchDiffLength && diffs.length != x + 1) {
+          // Small equality inside a patch.
+          patch.diffs[patchDiffLength++] = diffs[x];
+          patch.length1 += diff_text.length;
+          patch.length2 += diff_text.length;
+        } else if (diff_text.length >= 2 * this.Patch_Margin) {
+          // Time for a new patch.
+          if (patchDiffLength) {
+            this.patch_addContext_(patch, prepatch_text);
+            patches.push(patch);
+            patch = new diff_match_patch.patch_obj();
+            patchDiffLength = 0;
+            // Unlike Unidiff, our patch lists have a rolling context.
+            // http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
+            // Update prepatch text & pos to reflect the application of the
+            // just completed patch.
+            prepatch_text = postpatch_text;
+            char_count1 = char_count2;
+          }
+        }
+        break;
+    }
+
+    // Update the current character count.
+    if (diff_type !== DIFF_INSERT) {
+      char_count1 += diff_text.length;
+    }
+    if (diff_type !== DIFF_DELETE) {
+      char_count2 += diff_text.length;
+    }
+  }
+  // Pick up the leftover patch if not empty.
+  if (patchDiffLength) {
+    this.patch_addContext_(patch, prepatch_text);
+    patches.push(patch);
+  }
+
+  return patches;
+};
+
+
+/**
+ * Given an array of patches, return another array that is identical.
+ * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
+ * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
+ */
+diff_match_patch.prototype.patch_deepCopy = function(patches) {
+  // Making deep copies is hard in JavaScript.
+  var patchesCopy = [];
+  for (var x = 0; x < patches.length; x++) {
+    var patch = patches[x];
+    var patchCopy = new diff_match_patch.patch_obj();
+    patchCopy.diffs = [];
+    for (var y = 0; y < patch.diffs.length; y++) {
+      patchCopy.diffs[y] = patch.diffs[y].slice();
+    }
+    patchCopy.start1 = patch.start1;
+    patchCopy.start2 = patch.start2;
+    patchCopy.length1 = patch.length1;
+    patchCopy.length2 = patch.length2;
+    patchesCopy[x] = patchCopy;
+  }
+  return patchesCopy;
+};
+
+
+/**
+ * Merge a set of patches onto the text.  Return a patched text, as well
+ * as a list of true/false values indicating which patches were applied.
+ * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
+ * @param {string} text Old text.
+ * @return {!Array.<string|!Array.<boolean>>} Two element Array, containing the
+ *      new text and an array of boolean values.
+ */
+diff_match_patch.prototype.patch_apply = function(patches, text) {
+  if (patches.length == 0) {
+    return [text, []];
+  }
+
+  // Deep copy the patches so that no changes are made to originals.
+  patches = this.patch_deepCopy(patches);
+
+  var nullPadding = this.patch_addPadding(patches);
+  text = nullPadding + text + nullPadding;
+
+  this.patch_splitMax(patches);
+  // delta keeps track of the offset between the expected and actual location
+  // of the previous patch.  If there are patches expected at positions 10 and
+  // 20, but the first patch was found at 12, delta is 2 and the second patch
+  // has an effective expected position of 22.
+  var delta = 0;
+  var results = [];
+  for (var x = 0; x < patches.length; x++) {
+    var expected_loc = patches[x].start2 + delta;
+    var text1 = this.diff_text1(patches[x].diffs);
+    var start_loc;
+    var end_loc = -1;
+    if (text1.length > this.Match_MaxBits) {
+      // patch_splitMax will only provide an oversized pattern in the case of
+      // a monster delete.
+      start_loc = this.match_main(text, text1.substring(0, this.Match_MaxBits),
+                                  expected_loc);
+      if (start_loc != -1) {
+        end_loc = this.match_main(text,
+            text1.substring(text1.length - this.Match_MaxBits),
+            expected_loc + text1.length - this.Match_MaxBits);
+        if (end_loc == -1 || start_loc >= end_loc) {
+          // Can't find valid trailing context.  Drop this patch.
+          start_loc = -1;
+        }
+      }
+    } else {
+      start_loc = this.match_main(text, text1, expected_loc);
+    }
+    if (start_loc == -1) {
+      // No match found.  :(
+      results[x] = false;
+      // Subtract the delta for this failed patch from subsequent patches.
+      delta -= patches[x].length2 - patches[x].length1;
+    } else {
+      // Found a match.  :)
+      results[x] = true;
+      delta = start_loc - expected_loc;
+      var text2;
+      if (end_loc == -1) {
+        text2 = text.substring(start_loc, start_loc + text1.length);
+      } else {
+        text2 = text.substring(start_loc, end_loc + this.Match_MaxBits);
+      }
+      if (text1 == text2) {
+        // Perfect match, just shove the replacement text in.
+        text = text.substring(0, start_loc) +
+               this.diff_text2(patches[x].diffs) +
+               text.substring(start_loc + text1.length);
+      } else {
+        // Imperfect match.  Run a diff to get a framework of equivalent
+        // indices.
+        var diffs = this.diff_main(text1, text2, false);
+        if (text1.length > this.Match_MaxBits &&
+            this.diff_levenshtein(diffs) / text1.length >
+            this.Patch_DeleteThreshold) {
+          // The end points match, but the content is unacceptably bad.
+          results[x] = false;
+        } else {
+          this.diff_cleanupSemanticLossless(diffs);
+          var index1 = 0;
+          var index2;
+          for (var y = 0; y < patches[x].diffs.length; y++) {
+            var mod = patches[x].diffs[y];
+            if (mod[0] !== DIFF_EQUAL) {
+              index2 = this.diff_xIndex(diffs, index1);
+            }
+            if (mod[0] === DIFF_INSERT) {  // Insertion
+              text = text.substring(0, start_loc + index2) + mod[1] +
+                     text.substring(start_loc + index2);
+            } else if (mod[0] === DIFF_DELETE) {  // Deletion
+              text = text.substring(0, start_loc + index2) +
+                     text.substring(start_loc + this.diff_xIndex(diffs,
+                         index1 + mod[1].length));
+            }
+            if (mod[0] !== DIFF_DELETE) {
+              index1 += mod[1].length;
+            }
+          }
+        }
+      }
+    }
+  }
+  // Strip the padding off.
+  text = text.substring(nullPadding.length, text.length - nullPadding.length);
+  return [text, results];
+};
+
+
+/**
+ * Add some padding on text start and end so that edges can match something.
+ * Intended to be called only from within patch_apply.
+ * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
+ * @return {string} The padding string added to each side.
+ */
+diff_match_patch.prototype.patch_addPadding = function(patches) {
+  var paddingLength = this.Patch_Margin;
+  var nullPadding = '';
+  for (var x = 1; x <= paddingLength; x++) {
+    nullPadding += String.fromCharCode(x);
+  }
+
+  // Bump all the patches forward.
+  for (var x = 0; x < patches.length; x++) {
+    patches[x].start1 += paddingLength;
+    patches[x].start2 += paddingLength;
+  }
+
+  // Add some padding on start of first diff.
+  var patch = patches[0];
+  var diffs = patch.diffs;
+  if (diffs.length == 0 || diffs[0][0] != DIFF_EQUAL) {
+    // Add nullPadding equality.
+    diffs.unshift([DIFF_EQUAL, nullPadding]);
+    patch.start1 -= paddingLength;  // Should be 0.
+    patch.start2 -= paddingLength;  // Should be 0.
+    patch.length1 += paddingLength;
+    patch.length2 += paddingLength;
+  } else if (paddingLength > diffs[0][1].length) {
+    // Grow first equality.
+    var extraLength = paddingLength - diffs[0][1].length;
+    diffs[0][1] = nullPadding.substring(diffs[0][1].length) + diffs[0][1];
+    patch.start1 -= extraLength;
+    patch.start2 -= extraLength;
+    patch.length1 += extraLength;
+    patch.length2 += extraLength;
+  }
+
+  // Add some padding on end of last diff.
+  patch = patches[patches.length - 1];
+  diffs = patch.diffs;
+  if (diffs.length == 0 || diffs[diffs.length - 1][0] != DIFF_EQUAL) {
+    // Add nullPadding equality.
+    diffs.push([DIFF_EQUAL, nullPadding]);
+    patch.length1 += paddingLength;
+    patch.length2 += paddingLength;
+  } else if (paddingLength > diffs[diffs.length - 1][1].length) {
+    // Grow last equality.
+    var extraLength = paddingLength - diffs[diffs.length - 1][1].length;
+    diffs[diffs.length - 1][1] += nullPadding.substring(0, extraLength);
+    patch.length1 += extraLength;
+    patch.length2 += extraLength;
+  }
+
+  return nullPadding;
+};
+
+
+/**
+ * Look through the patches and break up any which are longer than the maximum
+ * limit of the match algorithm.
+ * Intended to be called only from within patch_apply.
+ * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
+ */
+diff_match_patch.prototype.patch_splitMax = function(patches) {
+  var patch_size = this.Match_MaxBits;
+  for (var x = 0; x < patches.length; x++) {
+    if (patches[x].length1 <= patch_size) {
+      continue;
+    }
+    var bigpatch = patches[x];
+    // Remove the big old patch.
+    patches.splice(x--, 1);
+    var start1 = bigpatch.start1;
+    var start2 = bigpatch.start2;
+    var precontext = '';
+    while (bigpatch.diffs.length !== 0) {
+      // Create one of several smaller patches.
+      var patch = new diff_match_patch.patch_obj();
+      var empty = true;
+      patch.start1 = start1 - precontext.length;
+      patch.start2 = start2 - precontext.length;
+      if (precontext !== '') {
+        patch.length1 = patch.length2 = precontext.length;
+        patch.diffs.push([DIFF_EQUAL, precontext]);
+      }
+      while (bigpatch.diffs.length !== 0 &&
+             patch.length1 < patch_size - this.Patch_Margin) {
+        var diff_type = bigpatch.diffs[0][0];
+        var diff_text = bigpatch.diffs[0][1];
+        if (diff_type === DIFF_INSERT) {
+          // Insertions are harmless.
+          patch.length2 += diff_text.length;
+          start2 += diff_text.length;
+          patch.diffs.push(bigpatch.diffs.shift());
+          empty = false;
+        } else if (diff_type === DIFF_DELETE && patch.diffs.length == 1 &&
+                   patch.diffs[0][0] == DIFF_EQUAL &&
+                   diff_text.length > 2 * patch_size) {
+          // This is a large deletion.  Let it pass in one chunk.
+          patch.length1 += diff_text.length;
+          start1 += diff_text.length;
+          empty = false;
+          patch.diffs.push([diff_type, diff_text]);
+          bigpatch.diffs.shift();
+        } else {
+          // Deletion or equality.  Only take as much as we can stomach.
+          diff_text = diff_text.substring(0,
+              patch_size - patch.length1 - this.Patch_Margin);
+          patch.length1 += diff_text.length;
+          start1 += diff_text.length;
+          if (diff_type === DIFF_EQUAL) {
+            patch.length2 += diff_text.length;
+            start2 += diff_text.length;
+          } else {
+            empty = false;
+          }
+          patch.diffs.push([diff_type, diff_text]);
+          if (diff_text == bigpatch.diffs[0][1]) {
+            bigpatch.diffs.shift();
+          } else {
+            bigpatch.diffs[0][1] =
+                bigpatch.diffs[0][1].substring(diff_text.length);
+          }
+        }
+      }
+      // Compute the head context for the next patch.
+      precontext = this.diff_text2(patch.diffs);
+      precontext =
+          precontext.substring(precontext.length - this.Patch_Margin);
+      // Append the end context for this patch.
+      var postcontext = this.diff_text1(bigpatch.diffs)
+                            .substring(0, this.Patch_Margin);
+      if (postcontext !== '') {
+        patch.length1 += postcontext.length;
+        patch.length2 += postcontext.length;
+        if (patch.diffs.length !== 0 &&
+            patch.diffs[patch.diffs.length - 1][0] === DIFF_EQUAL) {
+          patch.diffs[patch.diffs.length - 1][1] += postcontext;
+        } else {
+          patch.diffs.push([DIFF_EQUAL, postcontext]);
+        }
+      }
+      if (!empty) {
+        patches.splice(++x, 0, patch);
+      }
+    }
+  }
+};
+
+
+/**
+ * Take a list of patches and return a textual representation.
+ * @param {!Array.<!diff_match_patch.patch_obj>} patches Array of Patch objects.
+ * @return {string} Text representation of patches.
+ */
+diff_match_patch.prototype.patch_toText = function(patches) {
+  var text = [];
+  for (var x = 0; x < patches.length; x++) {
+    text[x] = patches[x];
+  }
+  return text.join('');
+};
+
+
+/**
+ * Parse a textual representation of patches and return a list of Patch objects.
+ * @param {string} textline Text representation of patches.
+ * @return {!Array.<!diff_match_patch.patch_obj>} Array of Patch objects.
+ * @throws {!Error} If invalid input.
+ */
+diff_match_patch.prototype.patch_fromText = function(textline) {
+  var patches = [];
+  if (!textline) {
+    return patches;
+  }
+  var text = textline.split('\n');
+  var textPointer = 0;
+  var patchHeader = /^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$/;
+  while (textPointer < text.length) {
+    var m = text[textPointer].match(patchHeader);
+    if (!m) {
+      throw new Error('Invalid patch string: ' + text[textPointer]);
+    }
+    var patch = new diff_match_patch.patch_obj();
+    patches.push(patch);
+    patch.start1 = parseInt(m[1], 10);
+    if (m[2] === '') {
+      patch.start1--;
+      patch.length1 = 1;
+    } else if (m[2] == '0') {
+      patch.length1 = 0;
+    } else {
+      patch.start1--;
+      patch.length1 = parseInt(m[2], 10);
+    }
+
+    patch.start2 = parseInt(m[3], 10);
+    if (m[4] === '') {
+      patch.start2--;
+      patch.length2 = 1;
+    } else if (m[4] == '0') {
+      patch.length2 = 0;
+    } else {
+      patch.start2--;
+      patch.length2 = parseInt(m[4], 10);
+    }
+    textPointer++;
+
+    while (textPointer < text.length) {
+      var sign = text[textPointer].charAt(0);
+      try {
+        var line = decodeURI(text[textPointer].substring(1));
+      } catch (ex) {
+        // Malformed URI sequence.
+        throw new Error('Illegal escape in patch_fromText: ' + line);
+      }
+      if (sign == '-') {
+        // Deletion.
+        patch.diffs.push([DIFF_DELETE, line]);
+      } else if (sign == '+') {
+        // Insertion.
+        patch.diffs.push([DIFF_INSERT, line]);
+      } else if (sign == ' ') {
+        // Minor equality.
+        patch.diffs.push([DIFF_EQUAL, line]);
+      } else if (sign == '@') {
+        // Start of next patch.
+        break;
+      } else if (sign === '') {
+        // Blank line?  Whatever.
+      } else {
+        // WTF?
+        throw new Error('Invalid patch mode "' + sign + '" in: ' + line);
+      }
+      textPointer++;
+    }
+  }
+  return patches;
+};
+
+
+/**
+ * Class representing one patch operation.
+ * @constructor
+ */
+diff_match_patch.patch_obj = function() {
+  /** @type {!Array.<!diff_match_patch.Diff>} */
+  this.diffs = [];
+  /** @type {?number} */
+  this.start1 = null;
+  /** @type {?number} */
+  this.start2 = null;
+  /** @type {number} */
+  this.length1 = 0;
+  /** @type {number} */
+  this.length2 = 0;
+};
+
+
+/**
+ * Emmulate GNU diff's format.
+ * Header: @@ -382,8 +481,9 @@
+ * Indicies are printed as 1-based, not 0-based.
+ * @return {string} The GNU diff string.
+ */
+diff_match_patch.patch_obj.prototype.toString = function() {
+  var coords1, coords2;
+  if (this.length1 === 0) {
+    coords1 = this.start1 + ',0';
+  } else if (this.length1 == 1) {
+    coords1 = this.start1 + 1;
+  } else {
+    coords1 = (this.start1 + 1) + ',' + this.length1;
+  }
+  if (this.length2 === 0) {
+    coords2 = this.start2 + ',0';
+  } else if (this.length2 == 1) {
+    coords2 = this.start2 + 1;
+  } else {
+    coords2 = (this.start2 + 1) + ',' + this.length2;
+  }
+  var text = ['@@ -' + coords1 + ' +' + coords2 + ' @@\n'];
+  var op;
+  // Escape the body of the patch with %xx notation.
+  for (var x = 0; x < this.diffs.length; x++) {
+    switch (this.diffs[x][0]) {
+      case DIFF_INSERT:
+        op = '+';
+        break;
+      case DIFF_DELETE:
+        op = '-';
+        break;
+      case DIFF_EQUAL:
+        op = ' ';
+        break;
+    }
+    text[x + 1] = op + encodeURI(this.diffs[x][1]) + '\n';
+  }
+  return text.join('').replace(/%20/g, ' ');
+};
+
+
+// Export these global variables so that they survive Google's JS compiler.
+// In a browser, 'this' will be 'window'.
+// Users of node.js should 'require' the uncompressed version since Google's
+// JS compiler may break the following exports for non-browser environments.
+this['diff_match_patch'] = diff_match_patch;
+this['DIFF_DELETE'] = DIFF_DELETE;
+this['DIFF_INSERT'] = DIFF_INSERT;
+this['DIFF_EQUAL'] = DIFF_EQUAL;
diff --git a/packages/test-in-browser/driver.css b/packages/test-in-browser/driver.css
index 897ab9dbe7..7b9bf2fb95 100644
--- a/packages/test-in-browser/driver.css
+++ b/packages/test-in-browser/driver.css
@@ -132,3 +132,18 @@ body {
     top: 10px;
     z-index: 2;
 }
+
+.string_equal {
+  line-height: 1.2;
+  margin-left: 30px;
+}
+.string_equal ins {
+  text-decoration: none;
+}
+.string_equal_expected ins {
+  background: #fe0;
+}
+.string_equal_actual ins {
+  color: #d00;
+  background: #fcc;
+}
diff --git a/packages/test-in-browser/driver.js b/packages/test-in-browser/driver.js
index 0d200cdfd3..cc891a7643 100644
--- a/packages/test-in-browser/driver.js
+++ b/packages/test-in-browser/driver.js
@@ -458,46 +458,81 @@ Template.event.events({
   }
 });
 
-Template.event.get_details = function() {
-
-  var prepare = function(details) {
-    return _.compact(_.map(details, function(val, key) {
-
-      // You can end up with a an undefined value, e.g. using
-      // isNull without providing a message attribute: isNull(1).
-      // No need to display those.
-      if (!_.isUndefined(val)) {
-        return {
-          key: key,
-          val: val
-        };
-      } else {
-        return undefined;
-      }
-    }));
-  };
-
-  var details = this.details;
-
-  if (! details) {
-    return null;
-  } else {
-
-    var type = details.type;
-    var stack = details.stack;
-
-    details = _.clone(details);
-    delete details.type;
-    delete details.stack;
-
-    return {
-      type: type,
-      stack: stack,
-      details: prepare(details)
-    };
-  }
+// e.g. doDiff('abc', 'bcd') => [[-1, 'a'], [0, 'bc'], [1, 'd']]
+var doDiff = function (str1, str2) {
+  var D = new diff_match_patch();
+  var pieces = D.diff_main(str1, str2, false);
+  D.diff_cleanupSemantic(pieces);
+  return pieces;
 };
 
+Template.event.helpers({
+  get_details: function() {
+
+    var details = this.details;
+
+    if (! details) {
+      return null;
+    } else {
+
+      var type = details.type;
+      var stack = details.stack;
+
+      details = _.clone(details);
+      delete details.type;
+      delete details.stack;
+      var prepare = function(details) {
+        if (type === 'string_equal') {
+          var diff = doDiff(details.actual,
+                            details.expected);
+        }
+
+        return _.compact(_.map(details, function(val, key) {
+
+          // make test._stringEqual results print nicely,
+          // in particular for multiline strings
+          if (type === 'string_equal' &&
+              (key === 'actual' || key === 'expected')) {
+            var html = '<pre class="string_equal string_equal_'+key+'">';
+          _.each(diff, function (piece) {
+            var which = piece[0];
+            var text = piece[1];
+            if (which === 0 ||
+                which === (key === 'actual' ? -1 : 1)) {
+              var htmlBit = Handlebars._escape(text).replace(
+                /\n/g, '<br>');
+              if (which !== 0)
+                htmlBit = '<ins>' + htmlBit + '</ins>';
+              html += htmlBit;
+            }
+          });
+          html += '</pre>';
+          val = new Handlebars.SafeString(html);
+          }
+
+          // You can end up with a an undefined value, e.g. using
+          // isNull without providing a message attribute: isNull(1).
+          // No need to display those.
+          if (!_.isUndefined(val)) {
+            return {
+              key: key,
+              val: val
+            };
+          } else {
+            return undefined;
+          }
+        }));
+      };
+
+      return {
+        type: type,
+        stack: stack,
+        details: prepare(details)
+      };
+    }
+  }
+});
+
 Template.event.is_debuggable = function() {
   return !!this.cookie;
 };
diff --git a/packages/test-in-browser/package.js b/packages/test-in-browser/package.js
index cfe84ca858..589ac3de4a 100644
--- a/packages/test-in-browser/package.js
+++ b/packages/test-in-browser/package.js
@@ -16,6 +16,8 @@ Package.on_use(function (api) {
 
   api.use(['spark', 'livedata', 'templating', 'deps'], 'client');
 
+  api.add_files('diff_match_patch_uncompressed.js', 'client');
+
   api.add_files([
     'driver.css',
     'driver.html',
diff --git a/packages/tinytest/tinytest.js b/packages/tinytest/tinytest.js
index de212efb50..74313762bd 100644
--- a/packages/tinytest/tinytest.js
+++ b/packages/tinytest/tinytest.js
@@ -107,6 +107,13 @@ _.extend(TestCaseResults.prototype, {
 
   // XXX eliminate 'message' and 'not' arguments
   equal: function (actual, expected, message, not) {
+
+    if ((! not) && (typeof actual === 'string') &&
+        (typeof expected === 'string')) {
+      this._stringEqual(actual, expected, message);
+      return;
+    }
+
     /* If expected is a DOM node, do a literal '===' comparison with
      * actual. Otherwise do a deep comparison, as implemented by _.isEqual.
      */
@@ -162,7 +169,7 @@ _.extend(TestCaseResults.prototype, {
   },
 
   // XXX nodejs assert.throws can take an expected error, as a class,
-  // regular expression, or predicate function.  However, with its 
+  // regular expression, or predicate function.  However, with its
   // implementation if a constructor (class) is passed in and `actual`
   // fails the instanceof test, the constructor is then treated as
   // a predicate and called with `actual` (!)
@@ -269,8 +276,23 @@ _.extend(TestCaseResults.prototype, {
     else
       this.fail({type: "length", expected: expected_length,
                  actual: obj.length});
+  },
+
+  // EXPERIMENTAL way to compare two strings that results in
+  // a nicer display in the test runner, e.g. for multiline
+  // strings
+  _stringEqual: function (actual, expected, message) {
+    if (actual !== expected) {
+      this.fail({type: "string_equal",
+                 message: message,
+                 expected: expected,
+                 actual: actual});
+    } else {
+      this.ok();
+    }
   }
 
+
 });
 
 /******************************************************************************/
diff --git a/tools/bundler.js b/tools/bundler.js
index e7ebee367a..fd9c563e0a 100644
--- a/tools/bundler.js
+++ b/tools/bundler.js
@@ -159,9 +159,9 @@
 // wait until later.
 
 var path = require('path');
+var util = require('util');
 var files = require(path.join(__dirname, 'files.js'));
 var packages = require(path.join(__dirname, 'packages.js'));
-var linker = require(path.join(__dirname, 'linker.js'));
 var Builder = require(path.join(__dirname, 'builder.js'));
 var archinfo = require(path.join(__dirname, 'archinfo.js'));
 var buildmessage = require('./buildmessage.js');
@@ -457,6 +457,11 @@ _.extend(Target.prototype, {
     // Link JavaScript and set up self.js, etc.
     self._emitResources();
 
+    // Preprocess and concatenate CSS files for client targets.
+    if (self instanceof ClientTarget) {
+      self.mergeCss();
+    }
+
     // Minify, if requested
     if (options.minify) {
       var minifiers = unipackage.load({
@@ -464,8 +469,11 @@ _.extend(Target.prototype, {
         packages: ['minifiers']
       }).minifiers;
       self.minifyJs(minifiers);
-      if (self.minifyCss) // XXX a bit of a hack
+
+      // CSS is minified only for client targets.
+      if (self instanceof ClientTarget) {
         self.minifyCss(minifiers);
+      }
     }
 
     if (options.addCacheBusters) {
@@ -669,7 +677,8 @@ _.extend(Target.prototype, {
             }
           }
 
-          if (resource.type === "js" && resource.sourceMap) {
+          // Both CSS and JS files can have source maps
+          if (resource.sourceMap) {
             f.setSourceMap(resource.sourceMap, path.dirname(relPath));
           }
 
@@ -753,9 +762,11 @@ var ClientTarget = function (options) {
   var self = this;
   Target.apply(this, arguments);
 
-  // CSS files. List of File. They will be loaded at page load in the
-  // order given.
+  // CSS files. List of File. They will be loaded in the order given.
   self.css = [];
+  // Cached CSS AST. If non-null, self.css has one item in it, processed CSS
+  // from merged input files, and this is its parse tree.
+  self._cssAstCache = null;
 
   // List of segments of additional HTML for <head>/<body>.
   self.head = [];
@@ -768,17 +779,88 @@ var ClientTarget = function (options) {
 inherits(ClientTarget, Target);
 
 _.extend(ClientTarget.prototype, {
+  // Lints CSS files and merges them into one file, fixing up source maps and
+  // pulling any @import directives up to the top since the CSS spec does not
+  // allow them to appear in the middle of a file.
+  mergeCss: function () {
+    var self = this;
+    var minifiers = unipackage.load({
+      library: self.library,
+      packages: ['minifiers']
+    }).minifiers;
+    var CssTools = minifiers.CssTools;
+
+    // Filenames passed to AST manipulator mapped to their original files
+    var originals = {};
+
+    var cssAsts = _.map(self.css, function (file) {
+      var filename = file.url.replace(/^\//, '');
+      originals[filename] = file;
+      try {
+        var parseOptions = { source: filename, position: true };
+        var ast = CssTools.parseCss(file.contents('utf8'), parseOptions);
+        ast.filename = filename;
+      } catch (e) {
+        buildmessage.error(e.message, { file: filename });
+        return { type: "stylesheet", stylesheet: { rules: [] },
+                 filename: filename };
+      }
+
+      return ast;
+    });
+
+    var warnCb = function (filename, msg) {
+      // XXX make this a buildmessage.warning call rather than a random log
+      console.log("%s: warn: %s", filename, msg);
+    };
+
+    // Other build phases might need this AST later
+    self._cssAstCache = CssTools.mergeCssAsts(cssAsts, warnCb);
+
+    // Overwrite the CSS files list with the new concatenated file
+    var stringifiedCss = CssTools.stringifyCss(self._cssAstCache,
+                                               { sourcemap: true });
+    self.css = [new File({ data: new Buffer(stringifiedCss.code, 'utf8') })];
+
+    // Add the contents of the input files to the source map of the new file
+    stringifiedCss.map.sourcesContent =
+      _.map(stringifiedCss.map.sources, function (filename) {
+        return originals[filename].contents('utf8');
+      });
+
+    // If any input files had source maps, apply them.
+    // Ex.: less -> css source map should be composed with css -> css source map
+    var newMap = sourcemap.SourceMapGenerator.fromSourceMap(
+      new sourcemap.SourceMapConsumer(stringifiedCss.map));
+
+    _.each(originals, function (file, name) {
+      if (! file.sourceMap)
+        return;
+      newMap.applySourceMap(
+        new sourcemap.SourceMapConsumer(file.sourceMap), name);
+    });
+
+    self.css[0].setSourceMap(JSON.stringify(newMap));
+    self.css[0].setUrlToHash(".css");
+  },
   // Minify the CSS in this target
   minifyCss: function (minifiers) {
     var self = this;
+    var minifiedCss = '';
 
-    var allCss = _.map(self.css, function (file) {
-      return file.contents('utf8');
-    }).join('\n');
+    // If there is an AST already calculated, don't waste time on parsing it
+    // again.
+    if (self._cssAstCache) {
+      minifiedCss = minifiers.CssTools.minifyCssAst(self._cssAstCache);
+    } else if (self.css) {
+      var allCss = _.map(self.css, function (file) {
+        return file.contents('utf8');
+      }).join('\n');
 
-    allCss = minifiers.CleanCSSProcess(allCss);
+      minifiedCss = minifiers.CssTools.minifyCss(allCss);
+    }
 
-    self.css = [new File({ data: new Buffer(allCss, 'utf8') })];
+    self.css = [new File({ data: new Buffer(minifiedCss, 'utf8') })];
     self.css[0].setUrlToHash(".css", "?meteor_css_resource=true");
   },