Re: Stitching together serieses

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

Konstantin Ryabitsev writes in commit 1718708bd211406cc60f6343b559fe02ad2be2a4:

Add --rethread flag for stitching unthreaded patch series

When submitters send patches without proper threading, maintainers
have no way to process them as a series with b4. Add a --rethread
flag to retrieval commands (am, shazam, mbox) and review track that
fetches unrelated messages and reconstitutes them into a properly
threaded series.

With a single message ID, b4 auto-discovers the rest of the series
by querying lore for patches from the same author within a 30-minute
window, matching by [PATCH n/m] counters and revision. With multiple
message IDs, b4 uses them directly. Stdin input is supported via
--rethread -.

When no cover letter is found, the first patch becomes the thread
root — the same structure as a normal coverless series on lore.
This avoids synthetic message IDs and keeps all outgoing references
(thank-you notes, trailers, review replies) pointing at real
messages on real mailing lists.

For review tracking, an is_rethreaded flag on the series table
(schema v7) gates the retrieval path so only rethreaded series use
the multi-fetch pipeline. The flag is persisted in the tracking
commit JSON so it survives database rebuilds via rescan. Member
patch information is stored in a new series_patches table for every
tracked series, laying the groundwork for future cherry-pick-at-
track-time support.

Key changes:
- Extract parse_msgid() from get_msgid() for reuse
- Add LoreSeries static methods for series reconstitution:
  identify_cover_letter(), rewrite_subject_counter(),
  renumber_patches(), rethread_messages(), rethread_series()
- Add discover_rethread_series() for auto-discovery from a
  single seed message using lore search (dt: time range queries)
- Add fetch_rethread_messages() and retrieve_rethreaded_messages()
- Hook into retrieve_messages() and review track's cmd_track()
- New series_patches table with (change_id, revision, position) PK
- New is_rethreaded column on series table for retrieval routing
- Persist is-rethreaded in tracking commit JSON; read it back in
  rescan_branches() and create_review_branch()
- retrieve_series_messages() gateway for review TUI retrieval
- ReviewApp._fetch_rethreaded_threads() for follow-up loading
- 45 tests covering parsing, renumbering, rethreading, discovery
  filtering, and integration with LoreMailbox
- Document --rethread in mbox, am/shazam, review, and man page

Closes: https://msgid.link/8637ff61-4eca-42ac-96fb-d530498b3f82@sirena.org.uk # 4958fdf
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Assisted-by: claude-opus-4-6

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