Add 'git cl diff' command.

This command shows the differences between local branch
and the last patch uploaded to rietveld. The idea being
that you can see what would be uploaded before you actually
upload.

This can useful when using 'git cl patch' to move changes
between checkouts and working from more than one machine at
once.

Review URL: https://chromiumcodereview.appspot.com/24276008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@225552 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -1861,7 +1861,18 @@ def CMDpatch(parser, args):
   # TODO(maruel): Use apply_issue.py
   # TODO(ukai): use gerrit-cherry-pick for gerrit repository?
 
-  if issue_arg.isdigit():
+  if options.newbranch:
+    if options.force:
+      RunGit(['branch', '-D', options.newbranch],
+          stderr=subprocess2.PIPE, error_ok=True)
+    RunGit(['checkout', '-b', options.newbranch,
+            Changelist().GetUpstreamBranch()])
+
+  return PatchIssue(issue_arg, options.reject, options.nocommit)
+
+
+def PatchIssue(issue_arg, reject, nocommit):
+  if type(issue_arg) is int or issue_arg.isdigit():
     # Input is an issue id.  Figure out the URL.
     issue = int(issue_arg)
     cl = Changelist(issue=issue)
@@ -1878,13 +1889,6 @@ def CMDpatch(parser, args):
     patchset = int(match.group(2))
     patch_data = urllib2.urlopen(issue_arg).read()
 
-  if options.newbranch:
-    if options.force:
-      RunGit(['branch', '-D', options.newbranch],
-          stderr=subprocess2.PIPE, error_ok=True)
-    RunGit(['checkout', '-b', options.newbranch,
-            Changelist().GetUpstreamBranch()])
-
   # Switch up to the top-level directory, if necessary, in preparation for
   # applying the patch.
   top = RunGit(['rev-parse', '--show-cdup']).strip()
@@ -1909,7 +1913,7 @@ def CMDpatch(parser, args):
   # pick up file adds.
   # The --index flag means: also insert into the index (so we catch adds).
   cmd = ['git', 'apply', '--index', '-p0']
-  if options.reject:
+  if reject:
     cmd.append('--reject')
   elif IsGitVersionAtLeast('1.7.12'):
     cmd.append('--3way')
@@ -1920,7 +1924,7 @@ def CMDpatch(parser, args):
     DieWithError('Failed to apply the patch')
 
   # If we had an issue, commit the current state and register the issue.
-  if not options.nocommit:
+  if not nocommit:
     RunGit(['commit', '-m', 'patch from issue %s' % issue])
     cl = Changelist()
     cl.SetIssue(issue)
@@ -2128,6 +2132,31 @@ def CMDset_close(parser, args):
   return 0
 
 
+def CMDdiff(parser, args):
+  """shows differences between local tree and last upload."""
+  cl = Changelist()
+  branch = cl.GetBranch()
+  TMP_BRANCH = 'git-cl-diff'
+  base_branch = RunGit(['merge-base', cl.GetUpstreamBranch(), 'HEAD']).strip()
+
+  # Create a new branch based on the merge-base
+  RunGit(['checkout', '-q', '-b', TMP_BRANCH, base_branch])
+  try:
+    # Patch in the latest changes from rietveld.
+    rtn = PatchIssue(cl.GetIssue(), False, False)
+    if rtn != 0:
+      return rtn
+
+    # Switch back to starting brand and diff against the temporary
+    # branch containing the latest rietveld patch.
+    subprocess2.check_call(['git', 'diff', TMP_BRANCH, branch])
+  finally:
+    RunGit(['checkout', '-q', branch])
+    RunGit(['branch', '-D', TMP_BRANCH])
+
+  return 0
+
+
 def CMDowners(parser, args):
   """interactively find the owners for reviewing"""
   parser.add_option(