Add line diff decorations to editor gutter

Added, modified, and deleted lines will now highlighted
in the gutter for files already checked in to the repository.

src/packages/git-diff/lib/git-diff-view.coffee

@@ -0,0 +1,62 @@
+_ = require 'underscore'
+
+module.exports =
+class GitDiffView
+  diffs: null
+  editor: null
+
+  constructor: (@editor) ->
+    @gutter = @editor.gutter
+    @diffs = {}
+
+    @editor.on 'editor:path-changed', => @subscribeToBuffer()
+    @editor.on 'editor:display-updated', => @renderDiffs()
+    git.on 'statuses-changed', =>
+      @diffs = {}
+      @scheduleDiffs()
+    git.on 'status-changed', (path) =>
+      delete @diffs[path]
+      @scheduleDiffs() if path is @editor.getPath()
+
+    @subscribeToBuffer()
+
+  subscribeToBuffer: ->
+    if @buffer?
+      @removeDiffs()
+      delete @diffs[@buffer.getPath()] if @buffer.destroyed
+      @buffer.off '.git-diff'
+      @buffer = null
+
+    if @buffer = @editor.getBuffer()
+      @scheduleDiffs() unless @diffs[@buffer.getPath()]?
+      @buffer.on 'contents-modified.git-diff', =>
+        @generateDiffs()
+        @renderDiffs()
+
+  scheduleDiffs: ->
+    _.nextTick =>
+      @generateDiffs()
+      @renderDiffs()
+
+  generateDiffs: ->
+    if path = @buffer.getPath()
+      @diffs[path] = git?.getLineDiffs(path, @buffer.getText())
+
+  removeDiffs: ->
+    @gutter.find('.line-number').removeClass('git-line-added git-line-modified git-line-removed')
+
+  renderDiffs: ->
+    return unless @gutter.isVisible()
+
+    @removeDiffs()
+
+    hunks = @diffs[@editor.getPath()] ? []
+    for hunk in hunks
+      if hunk.oldLines is 0 and hunk.newLines > 0
+        for row in [hunk.newStart...hunk.newStart + hunk.newLines]
+          @gutter.find(".line-number[lineNumber=#{row - 1}]").addClass('git-line-added')
+      else if hunk.newLines is 0 and hunk.oldLines > 0
+        @gutter.find(".line-number[lineNumber=#{hunk.newStart - 1}]").addClass('git-line-removed')
+      else
+        for row in [hunk.newStart...hunk.newStart + hunk.newLines]
+          @gutter.find(".line-number[lineNumber=#{row - 1}]").addClass('git-line-modified')

src/packages/git-diff/lib/git-diff.coffee

@@ -0,0 +1,12 @@
+GitDiffView = require './git-diff-view'
+
+module.exports =
+  configDefaults:
+    enabled: false
+
+  activate: ->
+    return unless git?
+    return unless config.get('git-diff.enabled')
+
+    rootView.eachEditor (editor) =>
+      new GitDiffView(editor) if git? and editor.getPane()?

src/packages/git-diff/package.cson

@@ -0,0 +1 @@
+'main': 'lib/git-diff'

src/packages/git-diff/spec/git-diff-spec.coffee

@@ -0,0 +1,63 @@
+RootView = require 'root-view'
+_ = require 'underscore'
+
+describe "GitDiff package", ->
+  editor = null
+
+  beforeEach ->
+    config.set('git-diff.enabled', true)
+    window.rootView = new RootView
+    rootView.attachToDom()
+    rootView.open('sample.js')
+    atom.activatePackage('git-diff')
+    editor = rootView.getActiveView()
+
+  describe "when the editor has modified lines", ->
+    it "highlights the modified lines", ->
+      expect(editor.find('.git-line-modified').length).toBe 0
+      editor.insertText('a')
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editor.find('.git-line-modified').length).toBe 1
+      expect(editor.find('.git-line-modified').attr('lineNumber')).toBe '0'
+
+  describe "when the editor has added lines", ->
+    it "highlights the added lines", ->
+      expect(editor.find('.git-line-added').length).toBe 0
+      editor.moveCursorToEndOfLine()
+      editor.insertNewline()
+      editor.insertText('a')
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editor.find('.git-line-added').length).toBe 1
+      expect(editor.find('.git-line-added').attr('lineNumber')).toBe '1'
+
+  describe "when the editor has removed lines", ->
+    it "highlights the line preceeding the deleted lines", ->
+      expect(editor.find('.git-line-added').length).toBe 0
+      editor.setCursorBufferPosition([5])
+      editor.deleteLine()
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editor.find('.git-line-removed').length).toBe 1
+      expect(editor.find('.git-line-removed').attr('lineNumber')).toBe '4'
+
+  describe "when a modified line is restored to the HEAD version contents", ->
+    it "removes the diff highlight", ->
+      expect(editor.find('.git-line-modified').length).toBe 0
+      editor.insertText('a')
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editor.find('.git-line-modified').length).toBe 1
+      editor.backspace()
+      advanceClock(editor.getBuffer().stoppedChangingDelay)
+      expect(editor.find('.git-line-modified').length).toBe 0
+
+  describe "when a modified file is opened", ->
+    it "highlights the changed lines", ->
+      path = project.resolve('sample.txt')
+      buffer = project.buildBuffer(path)
+      buffer.setText("Some different text.")
+      rootView.open('sample.txt')
+      nextTick = false
+      _.nextTick -> nextTick = true
+      waitsFor -> nextTick
+      runs ->
+        expect(editor.find('.git-line-modified').length).toBe 1
+        expect(editor.find('.git-line-modified').attr('lineNumber')).toBe '0'

src/packages/git-diff/stylesheets/git-diff.less

@@ -0,0 +1,11 @@
+.git-line-modified {
+  color: #f78a46;
+}
+
+.git-line-added {
+  color: #5293d8;
+}
+
+.git-line-removed {
+  color: #c41e3a;
+}