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 7ea39f73c95e80c86e10eb960241dc3e7683b76d..1b45aaeb5d9d40261dfe94e4a2ab9ca5581cfd07 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):
+    """Sets a tag for the current commit.
+
+    Assumptions: The commit already landed and the commit message is unique.
+    """
     raise NotImplementedError()
 
 
@@ -346,7 +350,7 @@ class GitSvnInterface(VCInterface):
     self.step.GitSVNTag(tag)
 
 
-class GitReadOnlyMixin(VCInterface):
+class GitTagsOnlyMixin(VCInterface):
   def Pull(self):
     self.step.GitPull()
 
@@ -375,8 +379,41 @@ class GitReadOnlyMixin(VCInterface):
       return "origin/%s" % name
     return "origin/branch-heads/%s" % name
 
-
-class GitReadSvnWriteInterface(GitReadOnlyMixin, GitSvnInterface):
+  def Tag(self, tag):
+    # 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")
+
+    # Find remote branch where current commit will appear. Assumes everything
+    # to be merge-free (unique parents).
+    branch = None
+    hsh = "HEAD"
+    while not branch:
+      branch = self.step.GitRemoteContains(hsh)
+      hsh += "^"

[agable, 2014/09/29 09:49:11]

Cute. Might be better to actually query Git for the parent of the commit and
directly reference that instead. Clearer logging too.

[Michael Achenbach, 2014/09/29 10:46:25]

Done. Changed the semantics slightly as HEAD always refers to a local commit
only.

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

[agable, 2014/09/29 09:49:11]

This n=1 is dangerous -- what if two commits get replicated in rapid succession?

[Michael Achenbach, 2014/09/29 10:46:25]

But shouldn't the grep on the unique title take care of this? Is there a better
command then git log for achieving the same thing?

+      if commit:
+        break
+      print("The commit is not replicated on git. Waiting for %s seconds." %

[agable, 2014/09/29 09:49:11]

nit: "...has not replicated to..."

[Michael Achenbach, 2014/09/29 10:46:25]

Done.

+            wait_interval)
+      self.step._side_effect_handler.Sleep(wait_interval)
+
+    if not commit:
+      self.step.Die("Couldn't determine commit for setting the tag. Maybe the "
+               "git updater is lacking behind?")

[agable, 2014/09/29 09:49:11]

nit: "lagging"

[agable, 2014/09/29 09:49:11]

nit: indentation

[Michael Achenbach, 2014/09/29 10:46:24]

Done.

[Michael Achenbach, 2014/09/29 10:46:24]

Done.

+
+    self.step.Git("tag %s %s" % (tag, commit))

[agable, 2014/09/29 09:49:11]

The fact that this takes args as a single string instead of a list of tokens
makes me very sad.

[Michael Achenbach, 2014/09/29 10:46:24]

I'm sad too. But I'll address this in a separate refactoring CL.

+    self.step.Git("push origin %s" % tag)
+
+
+class GitReadSvnWriteInterface(GitTagsOnlyMixin, GitSvnInterface):
   pass