Push version and changelog as a separate commit.

BUG=chromium:451357
LOG=n
TBR=tandrii@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/870923003

Cr-Commit-Position: refs/heads/master@{#26251}

tools/push-to-trunk/push_to_trunk.py

@@ -287,6 +287,28 @@ class ApplyChanges(Step):
     os.remove(self.Config("PATCH_FILE"))
 
 
+class CommitSquash(Step):
+  MESSAGE = "Commit to local candidates branch."
+
+  def RunStep(self):
+    # Make a first commit with a slightly different title to not confuse
+    # the tagging.
+    msg = FileToText(self.Config("COMMITMSG_FILE")).splitlines()
+    msg[0] = msg[0].replace("(based on", "(squashed - based on")
+    self.GitCommit(message = "\n".join(msg))
+
+
+class PrepareVersionBranch(Step):
+  MESSAGE = "Prepare new branch to commit version and changelog file."
+
+  def RunStep(self):
+    self.GitCheckout("master")
+    self.Git("fetch")
+    self.GitDeleteBranch(self.Config("TRUNKBRANCH"))
+    self.GitCreateBranch(self.Config("TRUNKBRANCH"),
+                         self.vc.RemoteCandidateBranch())
+
+
 class AddChangeLog(Step):
   MESSAGE = "Add ChangeLog changes to trunk branch."
 
@@ -312,8 +334,8 @@ class SetVersion(Step):
     self.SetVersion(os.path.join(self.default_cwd, VERSION_FILE), "new_")
 
 
-class CommitTrunk(Step):
-  MESSAGE = "Commit to local trunk branch."
+class CommitCandidate(Step):
+  MESSAGE = "Commit version and changelog to local candidates branch."
 
   def RunStep(self):
     self.GitCommit(file_name = self.Config("COMMITMSG_FILE"))
@@ -413,10 +435,13 @@ class PushToTrunk(ScriptsBase):
       SquashCommits,
       NewBranch,
       ApplyChanges,
+      CommitSquash,
+      SanityCheck,
+      Land,
+      PrepareVersionBranch,
       AddChangeLog,
       SetVersion,
-      CommitTrunk,
-      SanityCheck,
+      CommitCandidate,
       Land,
       TagRevision,
       CleanUp,

tools/push-to-trunk/test_scripts.py

@@ -719,6 +719,18 @@ Performance and stability improvements on all platforms."""
                os.path.join(TEST_CONFIG["DEFAULT_CWD"], CHANGELOG_FILE))
     os.environ["EDITOR"] = "vi"
 
+    commit_msg_squashed = """Version 3.22.5 (squashed - based on push_hash)
+
+Log text 1 (issue 321).
+
+Performance and stability improvements on all platforms."""
+
+    commit_msg = """Version 3.22.5 (based on push_hash)
+
+Log text 1 (issue 321).
+
+Performance and stability improvements on all platforms."""
+
     def ResetChangeLog():
       """On 'git co -b new_branch svn/trunk', and 'git checkout -- ChangeLog',
       the ChangLog will be reset to its content on trunk."""
@@ -732,14 +744,9 @@ Performance and stability improvements on all platforms."""
       ResetChangeLog()
       self.WriteFakeVersionFile()
 
-    def CheckSVNCommit():
+    def CheckVersionCommit():
       commit = FileToText(TEST_CONFIG["COMMITMSG_FILE"])
-      self.assertEquals(
-"""Version 3.22.5 (based on push_hash)
-
-Log text 1 (issue 321).
-
-Performance and stability improvements on all platforms.""", commit)
+      self.assertEquals(commit_msg, commit)
       version = FileToText(
           os.path.join(TEST_CONFIG["DEFAULT_CWD"], VERSION_FILE))
       self.assertTrue(re.search(r"#define MINOR_VERSION\s+22", version))
@@ -808,16 +815,23 @@ Performance and stability improvements on all platforms.""", commit)
       Cmd(("git new-branch %s --upstream origin/candidates" %
            TEST_CONFIG["TRUNKBRANCH"]), "", cb=ResetToTrunk),
       Cmd("git apply --index --reject \"%s\"" % TEST_CONFIG["PATCH_FILE"], ""),
+      Cmd("git commit -am \"%s\"" % commit_msg_squashed, ""),
+    ]
+    if manual:
+      expectations.append(RL("Y"))  # Sanity check.
+    expectations += [
+      Cmd("git cl land -f --bypass-hooks", ""),
+      Cmd("git checkout -f master", ""),
+      Cmd("git fetch", ""),
+      Cmd("git branch -D %s" % TEST_CONFIG["TRUNKBRANCH"], ""),
+      Cmd(("git new-branch %s --upstream origin/candidates" %
+           TEST_CONFIG["TRUNKBRANCH"]), "", cb=ResetToTrunk),
       Cmd("git checkout -f origin/candidates -- ChangeLog", "",
           cb=ResetChangeLog),
       Cmd("git checkout -f origin/candidates -- src/version.cc", "",
           cb=self.WriteFakeVersionFile),
       Cmd("git commit -aF \"%s\"" % TEST_CONFIG["COMMITMSG_FILE"], "",
-          cb=CheckSVNCommit),
-    ]
-    if manual:
-      expectations.append(RL("Y"))  # Sanity check.
-    expectations += [
+          cb=CheckVersionCommit),
       Cmd("git cl land -f --bypass-hooks", ""),
       Cmd("git fetch", ""),
       Cmd("git log -1 --format=%H --grep="