Add tag write access to merge script.

tools/push-to-trunk/common_includes.py

Index: tools/push-to-trunk/common_includes.py
diff --git a/tools/push-to-trunk/common_includes.py b/tools/push-to-trunk/common_includes.py
index f015601a070b652b816dfe5e9e0f6814306a0cc6..b8d1620dbda0cf9868dd47ada80e78add574ab83 100644
--- a/tools/push-to-trunk/common_includes.py
+++ b/tools/push-to-trunk/common_includes.py
@@ -296,6 +296,10 @@ class VCInterface(object):
   # tag and commit are different remote commands, while in git we would commit
   # and tag locally and then push/land in one unique step.
   def Tag(self, tag, remote):
+    """Sets a tag for the current commit.
+
+    Assumptions: The commit already landed and the commit message is unique.
+    """
     raise NotImplementedError()
 
 
@@ -348,7 +352,7 @@ class GitSvnInterface(VCInterface):
     self.step.GitSVNTag(tag)
 
 
-class GitReadOnlyMixin(VCInterface):
+class GitTagsOnlyMixin(VCInterface):
   def Pull(self):
     self.step.GitPull()
 
@@ -377,8 +381,33 @@ class GitReadOnlyMixin(VCInterface):
       return "origin/%s" % name
     return "origin/branch-heads/%s" % name
 
-
-class GitReadSvnWriteInterface(GitReadOnlyMixin, GitSvnInterface):
+  def Tag(self, tag, remote):
+    # Title of the current commit (the local title and the title for committing
+    # is the same in all merge and push scripts).
+    title = self.step.GitLog(n=1, format="%s")
+
+    # Wait for the commit to appear. Assumes unique commit message titles (this
+    # is the case for all automated merge and push commits - also no title is
+    # the prefix of another title).
+    commit = None
+    for wait_interval in [3, 5, 10, 30]:

[tandrii(chromium), 2014/10/02 17:36:06]

not sure 48 seconds is enough, you probably know better anyways.

[Michael Achenbach, 2014/10/07 10:10:50]

Bumped it a little.

+      self.step.Git("fetch")
+      commit = self.step.GitLog(n=1, format="%H", grep=title, branch=remote)
+      if commit:

[tandrii(chromium), 2014/10/02 17:36:06]

Naturally, i'm not sure about assumption above the loop. So, I'd check the title
for equality here anyways.

[Michael Achenbach, 2014/10/07 10:10:50]

I don't need the assumption if I add the commit message/title to the api (which
I did now).

+        break
+      print("The commit has not replicated to git. Waiting for %s seconds." %
+            wait_interval)
+      self.step._side_effect_handler.Sleep(wait_interval)
+
+    if not commit:

[tandrii(chromium), 2014/10/02 17:36:06]

or just

else:

[Michael Achenbach, 2014/10/07 10:10:50]

Odd construct - but I love shorter code :)

+      self.step.Die("Couldn't determine commit for setting the tag. Maybe the "
+                    "git updater is lagging behind?")
+
+    self.step.Git("tag %s %s" % (tag, commit))
+    self.step.Git("push origin %s" % tag)
+
+
+class GitReadSvnWriteInterface(GitTagsOnlyMixin, GitSvnInterface):
   pass