Let release scripts determine version based on tags.

tools/release/common_includes.py

 #!/usr/bin/env python
 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
@@ skipping 27 matching lines @@
 import subprocess
 import sys
 import textwrap
 import time
 import urllib
 import urllib2
 
 from git_recipes import GitRecipesMixin
 from git_recipes import GitFailedException
 
 CHANGELOG_FILE = "ChangeLog"

[Michael Achenbach, 2015/01/27 11:39:03]

This was moved from push_to_candidates.

+PUSH_MSG_GIT_RE = re.compile(r".* \(based on (?P<git_rev>[a-fA-F0-9]+)\)$")
 VERSION_FILE = os.path.join("src", "version.cc")
 VERSION_RE = re.compile(r"^\d+\.\d+\.\d+(?:\.\d+)?$")
 
 # V8 base directory.
 V8_BASE = os.path.dirname(
     os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 
 def TextToFile(text, file_name):
   with open(file_name, "w") as f:
@@ skipping 531 matching lines @@
     except GitFailedException:
       self.WaitForResolvingConflicts(patch_file)
 
   def GetLatestVersion(self):
     # Use cached version if available.
     if self["latest_version"]:
       return self["latest_version"]
 
     # Make sure tags are fetched.
     self.Git("fetch origin +refs/tags/*:refs/tags/*")
-    version_parts = sorted(filter(VERSION_RE.match, self.vc.GetTags()),
-                           key=SortingKey, reverse=True)[0].split(".")
-    if len(version_parts) == 3:

[Michael Achenbach, 2015/01/27 11:39:03]

This was a mistake. The version is used to later checkout based on it. 
Therefore it needs to match the tag.

-      version_parts.append("0")
-    self["latest_version"] = ".".join(version_parts)
-    return self["latest_version"]
+    version = sorted(filter(VERSION_RE.match, self.vc.GetTags()),
+                     key=SortingKey, reverse=True)[0]
+    self["latest_version"] = version
+    return version
+
+  def GetLatestRelease(self):
+    """The latest release is the git hash of the latest tagged version.
+
+    This revision should be rolled into chromium.
+    """
+    latest_version = self.GetLatestVersion()
+
+    # The latest release.
+    latest_hash = self.GitLog(n=1, format="%H", branch=latest_version)
+    assert latest_hash
+    return latest_hash
+
+  def GetLatestReleaseBase(self):
+    """The latest release base is the latest revision that is covered in the
+    last change log file. It doesn't include cherry-picked patches.
+    """
+    latest_version = self.GetLatestVersion()
+
+    # Strip patch level if it exists.
+    latest_version = ".".join(latest_version.split(".")[:3])
+
+    # The latest release base.
+    latest_hash = self.GitLog(n=1, format="%H", branch=latest_version)
+    assert latest_hash
+
+    match = PUSH_MSG_GIT_RE.match(
+        self.GitLog(n=1, format="%s", git_hash=latest_hash))
+    if match:
+      # Legacy: In the old process there's one level of indirection. The
+      # version is on the candidates branch and points to the real release
+      # base on master through the commit message.
+      latest_hash = match.group("git_rev")
+    return latest_hash
 
   def FindLastCandidatesPush(
       self, parent_hash="", branch="", include_patches=False):
     push_pattern = "^Version [[:digit:]]*\.[[:digit:]]*\.[[:digit:]]*"
     if not include_patches:
       # Non-patched versions only have three numbers followed by the "(based
       # on...) comment."
       push_pattern += " (based"
     branch = "" if parent_hash else branch or self.vc.RemoteCandidateBranch()
     return self.GitLog(n=1, format="%H", grep=push_pattern,
@@ skipping 203 matching lines @@
     for (number, step_class) in enumerate([BootstrapStep] + step_classes):
       steps.append(MakeStep(step_class, number, self._state, self._config,
                             options, self._side_effect_handler))
     for step in steps[options.step:]:
       if step.Run():
         return 0
     return 0
 
   def Run(self, args=None):
     return self.RunSteps(self._Steps(), args)