Reset origin/HEAD when it points to master

This change tries resetting origin/HEAD when it points to master and the ref cannot be found. Post master->main migration, some cached repositories seem to point origin/HEAD to master.

Bug: 1418866
Change-Id: I83942901b105cace4d51deeac7e400f98d200168
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4296441
Reviewed-by: Fumitoshi Ukai <ukai@google.com>
Commit-Queue: Aravind Vasudevan <aravindvasudev@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -735,7 +735,19 @@ def _git_checkout(sln, sln_dir, revisions, refs, no_fetch_tags, git_cache_dir,
       # Note that the '--' argument is needed to ensure that git treats
       # 'pin or branch' as revision or ref, and not as file/directory which
       # happens to have the exact same name.
-      git('checkout', '--force', pin or branch, '--', cwd=sln_dir)
+      ref = pin or branch
+      try:
+        git('checkout', '--force', ref, '--', cwd=sln_dir)
+      except SubprocessFailed as e:
+        # TODO(crbug.com/1418866): master->main migration leaves some builders
+        # broken with outdated ref for origin/HEAD in cache. In this case,
+        # reset the ref and retry.
+        if ref != 'refs/remotes/origin/HEAD':
+          raise e
+
+        git('remote', 'set-head', '-a', 'origin', cwd=sln_dir)
+        git('checkout', '--force', ref, '--', cwd=sln_dir)
+
       git('clean', '-dff', cwd=sln_dir)
       return
     except SubprocessFailed as e: