[release] Make auto-push script recover after failed branch attempt

NOTRY=true

Bug: chromium:1018099
Change-Id: I14de41aac11220fedb58cda9bf5ce66424ff381c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1879932Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64557}

tools/release/create_release.py

@@ -135,6 +135,21 @@ class EditChangeLog(Step):
     TextToFile(changelog_entry, self.Config("CHANGELOG_ENTRY_FILE"))
 
 
+class DeleteBranchRef(Step):
+  MESSAGE = "Delete branch ref."
+
+  def RunStep(self):
+    cmd = "push origin :refs/heads/%s" % self["version"]
+    if self._options.dry_run:
+      print("Dry run. Command:\ngit %s" % cmd)
+    else:
+      try:
+        self.Git(cmd)
+      except Exception:
+        # Be forgiving if branch ref does not exist.
+        pass
+
+
 class PushBranchRef(Step):
   MESSAGE = "Create branch ref."
 
@@ -293,6 +308,7 @@ class CreateRelease(ScriptsBase):
       DetectLastRelease,
       PrepareChangeLog,
       EditChangeLog,
+      DeleteBranchRef,
       PushBranchRef,
       MakeBranch,
       AddChangeLog,

tools/release/test_scripts.py

@@ -926,6 +926,7 @@ TBR=reviewer@chromium.org"""
       Cmd("git log -1 --format=%s rev1", "Log text 1.\n"),
       Cmd("git log -1 --format=%B rev1", "Text\nLOG=YES\nBUG=v8:321\nText\n"),
       Cmd("git log -1 --format=%an rev1", "author1@chromium.org\n"),
+      Cmd("git push origin :refs/heads/3.22.5", ""),
       Cmd("git push origin push_hash:refs/heads/3.22.5", ""),
       Cmd("git reset --hard origin/master", ""),
       Cmd("git new-branch work-branch --upstream origin/3.22.5", ""),