Git footer fix for v8

Git footers doesn't seem to support v8, let alone know that trunk actually maps
to the candidate branch.  This should fix it.

BUG=
TBR=agable

Review URL: https://codereview.chromium.org/645183002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@292445 0039d316-1c4b-4281-b951-d872f2087c98

git_footers.py

@@ -81,6 +81,14 @@ def get_position(footers):
   if svn_commit:
     match = GIT_SVN_ID_PATTERN.match(svn_commit)
     assert match, 'Invalid git-svn-id value: %s' % svn_commit
+    # V8 has different semantics than Chromium.
+    if re.match(r'.*https?://v8\.googlecode\.com/svn/trunk',
+                match.group(1)):
+      return ('refs/heads/candidates', match.group(2))
+    if re.match(r'.*https?://v8\.googlecode\.com/svn/branches/bleeding_edge',
+                match.group(1)):
+      return ('refs/heads/master', match.group(2))
+
     # Assume that any trunk svn revision will match the commit-position
     # semantics.
     if re.match('.*/trunk.*$', match.group(1)):