Add line diff that is newline character aware

Fixes #68

Author: kpdecker

Diff for: README.md

@@ -39,6 +39,10 @@ or
 
     Returns a list of change objects (See below).
 
+* `JsDiff.diffLinesNL(oldStr, newStr[, callback])` - diffs two blocks of text, comparing line by line. This differs from `diffLines` in that the newline character is treated as a distinct token. This allows for changes to the newline structure to occur independently of the line content and to be treated as such. In general this is the more human friendly form of `diffLines` and `diffLines` is better suited for patches and other computer friendly output.
+
+    Returns a list of change objects (See below).
+
 * `JsDiff.diffSentences(oldStr, newStr[, callback])` - diffs two blocks of text, comparing sentence by sentence.
 
     Returns a list of change objects (See below).

Diff for: src/diff/line.js

@@ -1,12 +1,23 @@
 import Diff from './base';
 
+function tokenize(value) {
+  return value.split(/(\n|\r\n)/);
+}
+
+// Treats new line characters as separate, significant tokens
+export const nlTokenLineDiff = new Diff();
+nlTokenLineDiff.tokenize = tokenize;
+
+// Inlines new line characters into the diff result, thus, `restaurant\n` is different than `restaruant`
 export const lineDiff = new Diff();
+
+// Operates in a similar fashion to lineDiff, but whitespace other thing the the newline character is trimmed
 export const trimmedLineDiff = new Diff();
 trimmedLineDiff.ignoreTrim = true;
 
 lineDiff.tokenize = trimmedLineDiff.tokenize = function(value) {
   let retLines = [],
-      linesAndNewlines = value.split(/(\n|\r\n)/);
+      linesAndNewlines = tokenize(value);
 
   // Ignore the final empty token that occurs if the string ends with a new line
   if (!linesAndNewlines[linesAndNewlines.length - 1]) {
@@ -32,3 +43,4 @@ lineDiff.tokenize = trimmedLineDiff.tokenize = function(value) {
 
 export function diffLines(oldStr, newStr, callback) { return lineDiff.diff(oldStr, newStr, callback); }
 export function diffTrimmedLines(oldStr, newStr, callback) { return trimmedLineDiff.diff(oldStr, newStr, callback); }
+export function diffLinesNL(oldStr, newStr, callback) { return nlTokenLineDiff.diff(oldStr, newStr, callback); }

Diff for: test/diff/line.js

@@ -1,4 +1,4 @@
-import {diffLines, diffTrimmedLines} from '../../lib/diff/line';
+import {diffLines, diffTrimmedLines, diffLinesNL} from '../../lib/diff/line';
 import {convertChangesToXML} from '../../lib/convert/xml';
 
 import {expect} from 'chai';
@@ -77,4 +77,15 @@ describe('diff/line', function() {
       expect(convertChangesToXML(diffResult)).to.equal('line\r\n<del>old value\r\n</del><ins>new value\r\n</ins>line');
     });
   });
+
+  describe('#diffLinesNL', function() {
+    expect(diffLinesNL('restaurant', 'restaurant\n')).to.eql([
+      {value: 'restaurant', count: 1},
+      {value: '\n', count: 1, added: true, removed: undefined}
+    ]);
+    expect(diffLinesNL('restaurant', 'restaurant\nhello')).to.eql([
+      {value: 'restaurant', count: 1},
+      {value: '\nhello', count: 2, added: true, removed: undefined}
+    ]);
+  });
 });