Improve rename paths

* Identify smallest different sub path of the changed files paths and
highlight the changed part

sample/index.html

@@ -9,12 +9,12 @@
       Author: rtfpessoa
   -->
 
-  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.3.0/styles/github.min.css">
+  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.4.0/styles/github.min.css">
 
   <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.3/jquery.js"></script>
 
-  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.3.0/highlight.min.js"></script>
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.4.0/highlight.min.js"></script>
-  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.3.0/languages/scala.min.js"></script>
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.4.0/languages/scala.min.js"></script>
 
   <!-- diff2html -->
   <link rel="stylesheet" type="text/css" href="../dist/diff2html.css">
@@ -24,6 +24,12 @@
 
   <script>
     var lineDiffExample =
+      "--- a/src/my/really/big/path/sample.js\n" +
+      "+++ b/src/my/small/path/sample.js\n" +
+      "@@ -1 +1,2 @@\n" +
+      "-test\n" +
+      "+test1r\n" +
+      "+test2r\n" +
       'diff --git a/src/core/init.java b/src/core/init.java\n' +
       'index e49196a..50f310c 100644\n' +
       '--- a/src/core/init.java\n' +

src/printer-utils.js

@@ -11,6 +11,8 @@
   var utils = require('./utils.js').Utils;
   var Rematch = require('./rematch.js').Rematch;
 
+  var separator = '/';
+
   function PrinterUtils() {
   }
 
@@ -32,18 +34,65 @@
   };
 
   PrinterUtils.prototype.getDiffName = function(file) {
-    var oldFilename = file.oldName;
+    var oldFilename = unifyPath(file.oldName);
-    var newFilename = file.newName;
+    var newFilename = unifyPath(file.newName);
 
     if (oldFilename && newFilename && oldFilename !== newFilename && !isDevNullName(oldFilename) && !isDevNullName(newFilename)) {
-      return oldFilename + ' -> ' + newFilename;
+      var prefixPaths = [];
+      var suffixPaths = [];
+
+      var oldFilenameParts = oldFilename.split(separator);
+      var newFilenameParts = newFilename.split(separator);
+
+      var oldFilenamePartsSize = oldFilenameParts.length;
+      var newFilenamePartsSize = newFilenameParts.length;
+
+      var i = 0;
+      var j = oldFilenamePartsSize - 1;
+      var k = newFilenamePartsSize - 1;
+
+      while (i < j && i < k) {
+        if (oldFilenameParts[i] === newFilenameParts[i]) {
+          prefixPaths.push(newFilenameParts[i]);
+          i = i + 1;
+        } else {
+          break;
+        }
+      }
+
+      while (j > i && k > i) {
+        if (oldFilenameParts[j] === newFilenameParts[k]) {
+          suffixPaths.unshift(newFilenameParts[k]);
+          j = j - 1;
+          k = k - 1;
+        } else {
+          break;
+        }
+      }
+
+      var finalPrefix = prefixPaths.join(separator);
+      var finalSuffix = suffixPaths.join(separator);
+
+      var oldRemainingPath = oldFilenameParts.slice(i, j + 1).join(separator);
+      var newRemainingPath = newFilenameParts.slice(i, k + 1).join(separator);
+
+      if (finalPrefix.length && finalSuffix.length) {
+        return finalPrefix + separator + '{' + oldRemainingPath + ' → ' + newRemainingPath + '}' + separator + finalSuffix;
+      } else if (finalPrefix.length) {
+        return finalPrefix + separator + '{' + oldRemainingPath + ' → ' + newRemainingPath + '}';
+      } else if (finalSuffix.length) {
+        return '{' + oldRemainingPath + ' → ' + newRemainingPath + '}' + separator + finalSuffix;
+      } else {
+        return oldFilename + ' → ' + newFilename;
+      }
+
     } else if (newFilename && !isDevNullName(newFilename)) {
       return newFilename;
     } else if (oldFilename) {
       return oldFilename;
     }
 
-    return 'Unknown filename';
+    return 'unknown/file/path';
   };
 
   PrinterUtils.prototype.diffHighlight = function(diffLine1, diffLine2, config) {
@@ -128,6 +177,14 @@
     };
   };
 
+  function unifyPath(path) {
+    if (path) {
+      return path.replace('\\', '/');
+    } else {
+      return path;
+    }
+  }
+
   function isDevNullName(name) {
     return name.indexOf('dev/null') !== -1;
   }

test/printer-utils-tests.js

@@ -28,12 +28,33 @@ describe('Utils', function() {
       });
       assert.equal('sample.js', result);
     });
-    it('should generate the file name for a changed file and renamed', function() {
+    it('should generate the file name for a changed file and full rename', function() {
       var result = PrinterUtils.getDiffName({
         oldName: 'sample1.js',
         newName: 'sample2.js'
       });
-      assert.equal('sample1.js -> sample2.js', result);
+      assert.equal('sample1.js → sample2.js', result);
+    });
+    it('should generate the file name for a changed file and prefix rename', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'src/path/sample.js',
+        newName: 'source/path/sample.js'
+      });
+      assert.equal('{src → source}/path/sample.js', result);
+    });
+    it('should generate the file name for a changed file and suffix rename', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'src/path/sample1.js',
+        newName: 'src/path/sample2.js'
+      });
+      assert.equal('src/path/{sample1.js → sample2.js}', result);
+    });
+    it('should generate the file name for a changed file and middle rename', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'src/really/big/path/sample.js',
+        newName: 'src/small/path/sample.js'
+      });
+      assert.equal('src/{really/big → small}/path/sample.js', result);
     });
     it('should generate the file name for a deleted file', function() {
       var result = PrinterUtils.getDiffName({
@@ -49,9 +70,9 @@ describe('Utils', function() {
       });
       assert.equal('src/my/file.js', result);
     });
-    it('should generate handle undefined filenames', function() {
+    it('should generate handle undefined filename', function() {
       var result = PrinterUtils.getDiffName({});
-      assert.equal('Unknown filename', result);
+      assert.equal('unknown/file/path', result);
     });
   });