Make 'gcl diff emptychange' show nothing if given change, |emptychange|, doesn't contain files.

BUG=27243
TEST=Create change which contains no files and confirm 'gcl diff createdchange' doesn't output anything.

M      gcl.py

Review URL: http://codereview.chromium.org/388001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@31551 0039d316-1c4b-4281-b951-d872f2087c98

gcl.py

@@ -1283,6 +1283,8 @@ def main(argv=None):
   else:
     # Everything else that is passed into gcl we redirect to svn, after adding
     # the files. This allows commands such as 'gcl diff xxx' to work.
+    if command == "diff" and not change_info.GetFileNames():
+      return 0
     args =["svn", command]
     root = GetRepositoryRoot()
     args.extend([os.path.join(root, x) for x in change_info.GetFileNames()])