When splitting lines, keep leading whitespace on current line.

If we detect leading whitespace, we replace the next token with the
result of splitting the next token into two tokens, one containing any
leading whitespace and one with the rest. Then the leading whitespace
is added to the current line. When the second half of the split is
processed, it no longer has leading whitespace and is split to the next
line.

src/atom/line-wrapper.coffee

@@ -40,13 +40,26 @@ class LineWrapper
     length = 0
     screenLine = []
     while tokens.length
-      break if length + tokens[0].value.length > @maxLength
-      token = tokens.shift()
-      length += token.value.length
-      screenLine.push token
+      nextToken = tokens[0]
+      if length + nextToken.value.length > @maxLength
+        # keep any leading whitespace on current line
+        if match = /\b/.exec(nextToken.value)
+          if match.index > 0
+            tokens[0..0] = @splitTokenAt(nextToken, match.index)
+          else
+            break
+      nextToken = tokens.shift()
+      length += nextToken.value.length
+      screenLine.push nextToken
 
     [screenLine].concat @splitTokens(tokens)
 
+  splitTokenAt: (token, index) ->
+    { type, value} = token
+    value1 = value.substring(0, index)
+    value2 = value.substring(index)
+    [{value: value1, type }, {value: value2, type}]
+
   buildWrappedLineForBufferRow: (bufferRow) ->
     wordRegex = getWordRegex()
     line = @buffer.getLine(bufferRow)