Only use side-by-side for one-sided image diffs (fixes #56)

Author: danvk

testdata/images/left/delete.png

@@ -203,6 +203,10 @@ var ImageDiffModeSelector = React.createClass({
     changeHandler: React.PropTypes.func.isRequired
   },
   render: function() {
+    if (isOneSided(this.props.filePair)) {
+      return null;  // Only "side-by-side" makes sense for one-sided diffs.
+    }
+
     // Returns the text, optionally wrapped in a link and/or <b> tag.
     var linkOrB = (isLink, isB, val, text) => {
       var inner = isB ? <b>{text}</b> : text;
@@ -306,6 +310,9 @@ var ImageDiff = React.createClass({
   },
   render: function() {
     var mode = this.props.imageDiffMode;
+    if (isOneSided(this.props.filePair)) {
+      mode = 'side-by-side';  // Only one that makes sense for one-sided diffs.
+    }
     var component = {
       'side-by-side': ImageSideBySide,
       'blink': ImageBlinker,

testdata/images/right/add.png

@@ -39,3 +39,11 @@ function filePairDisplayName(filePair) {
 
   return out;
 }
+
+
+/**
+ * Checks whether the diff is one-sided, i.e. an add or delete.
+ */
+function isOneSided(filePair) {
+  return (filePair.type == 'add' || filePair.type == 'delete');
+}