Re: b4 feature request: run command before rewriting history

[B4 Bugbot <bugbot+b4@kernel.org>]

Konstantin Ryabitsev writes in commit bc6c4d853c7eace3b7f325cbd17dfe2d67760fb7:

prep: add pre/post history-rewrite hooks

Add two new configuration keys, prep-pre-rewrite-hook and
prep-post-rewrite-hook, that let users run a command before and after
any b4 operation that rewrites history on a prep branch.

The pre-hook runs before the rewrite and aborts the operation if it
exits non-zero.  The post-hook runs after a successful rewrite; a
non-zero exit is logged as a warning but does not undo anything.

The primary use case is Stacked Git: users can set
prep-pre-rewrite-hook to "stg commit --all" so that StGit's internal
state is cleared before b4 modifies the branch, and
prep-post-rewrite-hook to "stg repair" to re-sync afterwards.

Hooks are called around git-filter-repo runs in run_frf(), which
covers all history rewrites on existing prep branches: cover letter
updates, trailer updates, and reroll cover rewrites.

Key changes:
- New run_rewrite_hook() helper in ez.py
- Instrumented run_frf() with pre/post hooks around frf.run()
- Added 6 unit tests for the hook mechanism
- Documented both config keys in docs/config.rst

Suggested-by: Toke Høiland-Jørgensen <toke@toke.dk>
Closes: https://msgid.link/87ttdkrylx.fsf@toke.dk # 73df66c
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Assisted-by: claude-opus-4-6

--
Deet-doot-dot, I am a bot.
b4 bug tracker (bugspray 0.1-dev)