Gennady Tsitovich 6cc266569e git cl cherry-pick: Use base parameter to fix identical tree errors ...

The `git cl cherry-pick` command previously created chained CLs by
first cherry-picking a change onto the destination branch tip and then
rebasing the result onto the parent CL created in the previous step.

This approach failed when a sequence of cherry-picks resulted in an
intermediate state having an identical tree compared to its intended
base (e.g., commit 1 changes X->Y, commit 2 changes Y->X). Gerrit
would reject the second cherry-pick with an "identical tree" error
because the rebase is done after the cherry pick.

This change modifies the process to use the `base` parameter of the
Gerrit `cherrypick` REST API endpoint.

Changes:
- Modify `gerrit_util.CherryPick` to accept and pass an optional `base`
  commit hash in the API request body.
- Update `git_cl.CMDcherry_pick`:
  - Before each cherry-pick operation in the loop, fetch the commit hash
    of the latest patchset from the previously processed parent CL.
  - Pass this commit hash as the `base` parameter to `gerrit_util.CherryPick`.
  - Remove the subsequent, now redundant, call to `gerrit_util.RebaseChange`.

This ensures the correct parent commit is specified during the
cherry-pick operation itself, allowing Gerrit to handle the chaining
correctly and avoid failures caused by identical tree states in
intermediate steps.

Bug: 408388488
Change-Id: I84066d65bd6bb127b253bee6564dd0622148a0e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6433112
Commit-Queue: Gennady Tsitovich <gtsitovich@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

2025-04-04 11:44:55 -07:00

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