[PATCH v5 0/2] history: sign rewritten commits

History rewriting creates commits through two paths: the history commands write replacement commits directly, while the replay machinery recreates descendants above the rewritten range. Neither path currently honors `commit.gpgSign` or an explicit signing request, so rewriting signed history can leave the resulting commits unsigned.

Add a signing-key option to the replay API, then have the history commands pass the selected signer through both paths. Expose the standard `-S`/`--gpg-sign[=<key-id>]` and `--no-gpg-sign` options for `drop`, `fixup`, `reword`, `split`, and `squash`. This applies one signing policy to every commit created by the rewrite, including both commits from `split`, the commit from `squash`, and replayed descendants.

The behavior follows rebase, cherry-pick, and revert: `commit.gpgSign` supplies the default, command-line options override it, and the last command-line option wins. The signature attests the current committer's rewrite while preserving the original author identity.

Changes since v4:

 - Add Git completion coverage for `--gpg-sign` and `--no-gpg-sign` to the
   history subcommand option tests

Souma (2):
  replay: allow callers to sign commits
  history: sign rewritten commits

 Documentation/git-history.adoc | 18 +++++--
 builtin/history.c              | 96 +++++++++++++++++++++++++---------
 replay.c                       | 13 +++--
 replay.h                       |  6 +++
 t/t3451-history-reword.sh      | 63 ++++++++++++++++++++++
 t/t3452-history-split.sh       | 44 ++++++++++++++++
 t/t3453-history-fixup.sh       | 39 ++++++++++++++
 t/t3454-history-drop.sh        | 50 ++++++++++++++++++
 t/t3455-history-squash.sh      | 61 +++++++++++++++++++++
 t/t9902-completion.sh          |  2 +
 10 files changed, 358 insertions(+), 34 deletions(-)

Range-diff against v4:
1:  d45cce8e25 = 1:  d45cce8e25 replay: allow callers to sign commits
2:  8b4766fc0e ! 2:  65f3de1562 history: sign rewritten commits
    @@ t/t3455-history-squash.sh: check_commit_author () {
      test_expect_success 'setup linear history touching two files' '
      	test_commit base file a start &&
      	GIT_AUTHOR_NAME=One GIT_AUTHOR_EMAIL=one@example.com \
    +
    + ## t/t9902-completion.sh ##
    +@@ t/t9902-completion.sh: test_expect_success 'git history subcommand options' '
    + 	test_completion "git history split main --" <<-\EOF &&
    + 	--update-refs=Z
    + 	--dry-run Z
    ++	--gpg-sign Z
    ++	--no-... Z
    + 	--no-dry-run Z
    + 	EOF
    + 	test_completion "git history fixup --upd" "--update-refs=" &&