[PATCH v5 00/29] rebase: support --trailer

Li Chen
2025-10-22T05:40:13Z

From: Li Chen <chenl311@chinatelecom.cn>

This patch series teaches git rebase a new
--trailer <text> option and, as a prerequisite, moves all trailer
handling out of the external interpret-trailers helper and into the
builtin code path, as suggested by Phillip Wood.

Patch 0 switches trailer.c to an in-memory implementation
(amend_strbuf_with_trailers()). It removes every fork/exec.

Patch 1~8 fix all reviewer comments from v3 for patch 0.

Patch 9 builds on that helper to implement
git rebase --trailer. When the option is given we:
force the merge backend (apply/am backend lacks a message filter),
automatically enable --force-rebase so that fast-forwarded
commits are rewritten, and append the requested trailer(s) to every
rewritten commit.
State is stored in $state_dir/trailer so an interrupted rebase can
resume safely. A dedicated test-suite (t3440) exercises plain,
conflict, --root, invalid-input scenarios and etc.

The rest patches address all reviewer comments from v3 for patch 9.

All t/*.sh testcases have run successfully.

v5: fix all Kristoffer's review comments form v4[3] in place and without new patches.
v4: fix all reviewer comments in v3. [2], and add patch 1~8 & 10~29 to fix review comments.
v3: merges the remaining trailer paths into one in-process helper, dropping the
duplicate code, as pointed by Junio and Phillip [1]
v2: fix issues pointed by Phillip
RFC link: https://lore.kernel.org/git/196a5ac1393.f5b4db7d187309.2451613571977217927@linux.beauty/

Comments welcome!

[1]: https://lore.kernel.org/git/xmqq8qlzkukw.fsf@gitster.g/
[2]: https://lore.kernel.org/git/20250803150059.402017-1-me@linux.beauty/
[3]: https://lore.kernel.org/git/20251014122452.1851103-1-me@linux.beauty/

Li Chen (29):
trailer: append trailers in-process and drop the fork to
`interpret-trailers`
trailer: restore interpret_trailers helper
trailer: drop --trailer prefix handling in amend helper
trailer: move config_head and arg_head to if storage
trailer: use bool for had_trailer_before
interpret-trailers: buffer stdout output
trailer: mirror interpret-trailers output flow
trailer: handle trailer append failures gently
rebase: support --trailer
rebase: inline trailer state paths
rebase: reuse buffer for trailer args
rebase: drop redundant strbuf_release call
rebase: skip stripping of --trailer option prefix
rebase: die on invalid trailer args
rebase: validate trailers with configured separators
sequencer: add trailers to message before writing file
t3440: create expect files at point of use
t3440: check apply backend error includes option
t3440: use test_commit_message for trailer checks
t3440: drop redundant resets and pass branch to rebase where needed
t3440: assert trailer on HEAD after conflict rebase
rebase: persist --trailer options across restarts
t3440: remove redundant --keep-empty
t3440: use helper for trailer checks
t3440: test --trailer without values
t3440: convert ex.com to example.com
t3440: ensure trailers persist after rebase continue
t3440: exercise trailer config mapping
sequencer: honor --trailer with fixup -C

Documentation/git-rebase.adoc | 9 ++-
builtin/commit.c | 2 +-
builtin/interpret-trailers.c | 94 +++++-------------------
builtin/rebase.c | 50 +++++++++++++
builtin/tag.c | 3 +-
sequencer.c | 34 +++++++++
sequencer.h | 4 +-
t/meson.build | 1 +
t/t3440-rebase-trailer.sh | 134 ++++++++++++++++++++++++++++++++++
trailer.c | 130 ++++++++++++++++++++++++++++++---
trailer.h | 23 +++++-
wrapper.c | 16 ++++
wrapper.h | 6 ++
13 files changed, 412 insertions(+), 94 deletions(-)
create mode 100755 t/t3440-rebase-trailer.sh

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2.51.0