Ignore header content when applying patch

Fixes #49

Author: kpdecker

Diff for: diff.js

@@ -458,10 +458,16 @@
       applyPatch: function(oldStr, uniDiff) {
         var diffstr = uniDiff.split('\n');
         var diff = [];
-        var remEOFNL = false,
+        var i = 0,
+            remEOFNL = false,
             addEOFNL = false;
 
-        for (var i = (diffstr[0][0]==='I'?4:0); i < diffstr.length; i++) {
+        // Skip to the first change chunk
+        while (i < diffstr.length && !/^@@/.test(diffstr[i])) {
+          i++;
+        }
+
+        for (; i < diffstr.length; i++) {
           if (diffstr[i][0] === '@') {
             var meh = diffstr[i].split(/@@ -(\d+),(\d+) \+(\d+),(\d+) @@/);
             diff.unshift({

Diff for: test/applyPatch.js

@@ -269,4 +269,24 @@ describe('#applyPatch', function() {
       + '+++ testFileName\tNew Header\n';
     diff.applyPatch(oldFile, diffFile).should.equal(oldFile);
   });
+
+  it('should apply patches that lack an index header', function() {
+    diff.applyPatch(
+        'line2\n'+
+        'line3\n'+
+        'line5\n',
+
+        '--- test\theader1\n'
+        + '+++ test\theader2\n'
+        + '@@ -1,3 +1,4 @@\n'
+        + ' line2\n'
+        + ' line3\n'
+        + '+line4\n'
+        + ' line5\n')
+      .should.equal(
+        'line2\n'
+        + 'line3\n'
+        + 'line4\n'
+        + 'line5\n');
+  });
 });