Re: [PATCH] commit: add --committer option

>
> Hi ZheNing
>
> On 09/11/2025 10:22, ZheNing Hu via GitGitGadget wrote:
> > From: ZheNing Hu <adlternative@gmail.com>
> >
> >
> >      This patch introduces the --committer option to git-commit, providing:
> >
> >       1. Consistency with the existing --author option
> >       2. A more convenient alternative to environment variables
> >       3. Better support for automated workflows and scripts
> >       4. Improved user experience when managing multiple identities
>
> What's the use case for the same person committing under different
> identities? We already have a config mechanism to set different
> identities for different repositories but I'm struggling to see why
> someone would want to create commits under multiple identities in a
> single repository. For scripts it easy enough to set the relevant
> environment variables if a tool wants to create commits under its own
> identity.
>

> Thanks
>
> Phillip
>
> >      The implementation follows the same pattern as the --author option,
> >      accepting the format "Name " and properly validating the input.
> >
> > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1997%2Fadlternative%2Fzh%2Fimplement-committer-option-v1
> > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1997/adlternative/zh/implement-committer-option-v1
> > Pull-Request: https://github.com/gitgitgadget/git/pull/1997
> >
> >   Documentation/git-commit.adoc |  9 +++-
> >   builtin/commit.c              | 58 ++++++++++++++++++++++++-
> >   t/t7509-commit-authorship.sh  | 80 +++++++++++++++++++++++++++++++++++
> >   3 files changed, 144 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/git-commit.adoc b/Documentation/git-commit.adoc
> > index 54c207ad45..a015c8328e 100644
> > --- a/Documentation/git-commit.adoc
> > +++ b/Documentation/git-commit.adoc
> > @@ -12,7 +12,7 @@ git commit [-a | --interactive | --patch] [-s] [-v] [-u[<mode>]] [--amend]
> >          [--dry-run] [(-c | -C | --squash) <commit> | --fixup [(amend|reword):]<commit>]
> >          [-F <file> | -m <msg>] [--reset-author] [--allow-empty]
> >          [--allow-empty-message] [--no-verify] [-e] [--author=<author>]
> > -        [--date=<date>] [--cleanup=<mode>] [--[no-]status]
> > +        [--date=<date>] [--committer=<committer>] [--cleanup=<mode>] [--[no-]status]
> >          [-i | -o] [--pathspec-from-file=<file> [--pathspec-file-nul]]
> >          [(--trailer <token>[(=|:)<value>])...] [-S[<keyid>]]
> >          [--] [<pathspec>...]
> > @@ -181,6 +181,13 @@ See linkgit:git-rebase[1] for details.
> >   `--date=<date>`::
> >       Override the author date used in the commit.
> >
> > +`--committer=<committer>`::
> > +     Override the committer for the commit. Specify an explicit committer using the
> > +     standard `A U Thor <committer@example.com>` format. Otherwise _<committer>_
> > +     is assumed to be a pattern and is used to search for an existing
> > +     commit by that author (i.e. `git rev-list --all -i --author=<committer>`);
> > +     the commit author is then copied from the first such commit found.
> > +
> >   `-m <msg>`::
> >   `--message=<msg>`::
> >       Use _<msg>_ as the commit message.
> > diff --git a/builtin/commit.c b/builtin/commit.c
> > index 0243f17d53..88e77cbaab 100644
> > --- a/builtin/commit.c
> > +++ b/builtin/commit.c
> > @@ -49,7 +49,7 @@ static const char * const builtin_commit_usage[] = {
> >          "           [--dry-run] [(-c | -C | --squash) <commit> | --fixup [(amend|reword):]<commit>]\n"
> >          "           [-F <file> | -m <msg>] [--reset-author] [--allow-empty]\n"
> >          "           [--allow-empty-message] [--no-verify] [-e] [--author=<author>]\n"
> > -        "           [--date=<date>] [--cleanup=<mode>] [--[no-]status]\n"
> > +        "           [--date=<date>] [--committer=<committer>] [--cleanup=<mode>] [--[no-]status]\n"
> >          "           [-i | -o] [--pathspec-from-file=<file> [--pathspec-file-nul]]\n"
> >          "           [(--trailer <token>[(=|:)<value>])...] [-S[<keyid>]]\n"
> >          "           [--] [<pathspec>...]"),
> > @@ -112,6 +112,7 @@ static enum {
> >   } commit_style;
> >
> >   static const char *force_author;
> > +static const char *force_committer;
> >   static char *logfile;
> >   static char *template_file;
> >   /*
> > @@ -690,6 +691,48 @@ static void determine_author_info(struct strbuf *author_ident)
> >       free(date);
> >   }
> >
> > +static void determine_committer_info(struct strbuf *committer_ident)
> > +{
> > +     char *name, *email, *date;
> > +     struct ident_split committer;
> > +
> > +     name = xstrdup_or_null(getenv("GIT_COMMITTER_NAME"));
> > +     email = xstrdup_or_null(getenv("GIT_COMMITTER_EMAIL"));
> > +     date = xstrdup_or_null(getenv("GIT_COMMITTER_DATE"));
> > +
> > +     if (force_committer) {
> > +             struct ident_split ident;
> > +
> > +             if (split_ident_line(&ident, force_committer, strlen(force_committer)) < 0)
> > +                     die(_("malformed --committer parameter"));
> > +             set_ident_var(&name, xmemdupz(ident.name_begin, ident.name_end - ident.name_begin));
> > +             set_ident_var(&email, xmemdupz(ident.mail_begin, ident.mail_end - ident.mail_begin));
> > +
> > +             if (ident.date_begin) {
> > +                     struct strbuf date_buf = STRBUF_INIT;
> > +                     strbuf_addch(&date_buf, '@');
> > +                     strbuf_add(&date_buf, ident.date_begin, ident.date_end - ident.date_begin);
> > +                     strbuf_addch(&date_buf, ' ');
> > +                     strbuf_add(&date_buf, ident.tz_begin, ident.tz_end - ident.tz_begin);
> > +                     set_ident_var(&date, strbuf_detach(&date_buf, NULL));
> > +             }
> > +     }
> > +
> > +     if (force_date) {
> > +             struct strbuf date_buf = STRBUF_INIT;
> > +             if (parse_force_date(force_date, &date_buf))
> > +                     die(_("invalid date format: %s"), force_date);
> > +             set_ident_var(&date, strbuf_detach(&date_buf, NULL));
> > +     }
> > +
> > +     strbuf_addstr(committer_ident, fmt_ident(name, email, WANT_COMMITTER_IDENT, date,
> > +                             IDENT_STRICT));
> > +     assert_split_ident(&committer, committer_ident);
> > +     free(name);
> > +     free(email);
> > +     free(date);
> > +}
> > +
> >   static int author_date_is_interesting(void)
> >   {
> >       return author_message || force_date;
> > @@ -1321,6 +1364,9 @@ static int parse_and_validate_options(int argc, const char *argv[],
> >       if (force_author && renew_authorship)
> >               die(_("options '%s' and '%s' cannot be used together"), "--reset-author", "--author");
> >
> > +     if (force_committer && !strchr(force_committer, '>'))
> > +             force_committer = find_author_by_nickname(force_committer);
> > +
> >       if (logfile || have_option_m || use_message)
> >               use_editor = 0;
> >
> > @@ -1709,6 +1755,7 @@ int cmd_commit(int argc,
> >               OPT_FILENAME('F', "file", &logfile, N_("read message from file")),
> >               OPT_STRING(0, "author", &force_author, N_("author"), N_("override author for commit")),
> >               OPT_STRING(0, "date", &force_date, N_("date"), N_("override date for commit")),
> > +             OPT_STRING(0, "committer", &force_committer, N_("committer"), N_("override committer for commit")),
> >               OPT_CALLBACK('m', "message", &message, N_("message"), N_("commit message"), opt_parse_m),
> >               OPT_STRING('c', "reedit-message", &edit_message, N_("commit"), N_("reuse and edit message from specified commit")),
> >               OPT_STRING('C', "reuse-message", &use_message, N_("commit"), N_("reuse message from specified commit")),
> > @@ -1785,6 +1832,7 @@ int cmd_commit(int argc,
> >
> >       struct strbuf sb = STRBUF_INIT;
> >       struct strbuf author_ident = STRBUF_INIT;
> > +     struct strbuf committer_ident = STRBUF_INIT;
> >       const char *index_file, *reflog_msg;
> >       struct object_id oid;
> >       struct commit_list *parents = NULL;
> > @@ -1930,8 +1978,13 @@ int cmd_commit(int argc,
> >               append_merge_tag_headers(parents, &tail);
> >       }
> >
> > +     if (force_committer) {
> > +             determine_committer_info(&committer_ident);
> > +     }
> > +
> >       if (commit_tree_extended(sb.buf, sb.len, &the_repository->index->cache_tree->oid,
> > -                              parents, &oid, author_ident.buf, NULL,
> > +                              parents, &oid, author_ident.buf,
> > +                              force_committer ? committer_ident.buf : NULL,
> >                                sign_commit, extra)) {
> >               rollback_index_files();
> >               die(_("failed to write commit object"));
> > @@ -1980,6 +2033,7 @@ cleanup:
> >       free_commit_extra_headers(extra);
> >       free_commit_list(parents);
> >       strbuf_release(&author_ident);
> > +     strbuf_release(&committer_ident);
> >       strbuf_release(&err);
> >       strbuf_release(&sb);
> >       free(logfile);
> > diff --git a/t/t7509-commit-authorship.sh b/t/t7509-commit-authorship.sh
> > index 8e373b566b..45527f6a70 100755
> > --- a/t/t7509-commit-authorship.sh
> > +++ b/t/t7509-commit-authorship.sh
> > @@ -12,6 +12,11 @@ author_header () {
> >       sed -n -e '/^$/q' -e '/^author /p'
> >   }
> >
> > +committer_header () {
> > +     git cat-file commit "$1" |
> > +     sed -n -e '/^$/q' -e '/^committer /p'
> > +}
> > +
> >   message_body () {
> >       git cat-file commit "$1" |
> >       sed -e '1,/^$/d'
> > @@ -171,4 +176,79 @@ test_expect_success '--reset-author with CHERRY_PICK_HEAD' '
> >       test_cmp expect actual
> >   '
> >
> > +test_expect_success '--committer option overrides committer' '
> > +     git checkout Initial &&
> > +     echo "Test --committer" >>foo &&
> > +     test_tick &&
> > +     git commit -a -m "test committer" --committer="Custom Committer <custom@committer.example>" &&
> > +     committer_header HEAD >actual &&
> > +     grep "Custom Committer <custom@committer.example>" actual
> > +'
> > +
> > +test_expect_success '--committer with pattern search' '
> > +     echo "Test committer pattern" >>foo &&
> > +     test_tick &&
> > +     git commit -a -m "test committer pattern" --committer="Frigate" &&
> > +     committer_header HEAD >actual &&
> > +     grep "Frigate <flying@over.world>" actual
> > +'
> > +
> > +test_expect_success '--committer malformed parameter' '
> > +     echo "Test malformed" >>foo &&
> > +     test_tick &&
> > +     test_must_fail git commit -a -m "test malformed" --committer="malformed committer"
> > +'
> > +
> > +test_expect_success '--committer with --amend option' '
> > +     git checkout -f Initial &&
> > +     echo "Test committer with amend" >>foo &&
> > +     test_tick &&
> > +     git commit -a -m "initial commit for amend test" &&
> > +     echo "Modified for amend" >>foo &&
> > +     test_tick &&
> > +     git commit -a --amend --no-edit \
> > +             --author="Test Author <test@author.example>" \
> > +             --committer="Test Committer <test@committer.example>" &&
> > +     author_header HEAD >actual_author &&
> > +     grep "Test Author <test@author.example>" actual_author &&
> > +     committer_header HEAD >actual_committer &&
> > +     grep "Test Committer <test@committer.example>" actual_committer
> > +'
> > +
> > +test_expect_success 'GIT_COMMITTER_* environment variables' '
> > +     git checkout -f Initial &&
> > +     echo "Test env vars" >>foo &&
> > +     test_tick &&
> > +     GIT_COMMITTER_NAME="Env Committer" \
> > +     GIT_COMMITTER_EMAIL="env@test.example" \
> > +     git commit -a -m "test committer env vars" &&
> > +     committer_header HEAD >actual &&
> > +     grep "Env Committer <env@test.example>" actual
> > +'
> > +
> > +test_expect_success '--committer overrides GIT_COMMITTER_* environment variables' '
> > +     echo "Test override" >>foo &&
> > +     test_tick &&
> > +     GIT_COMMITTER_NAME="Env Committer" \
> > +     GIT_COMMITTER_EMAIL="env@test.example" \
> > +     git commit -a -m "test override" \
> > +             --committer="Override Committer <override@test.example>" &&
> > +     committer_header HEAD >actual &&
> > +     grep "Override Committer <override@test.example>" actual
> > +'
> > +
> > +test_expect_success '--date with --committer changes both author and committer dates' '
> > +     git checkout -f Initial &&
> > +     echo "Test date override" >>foo &&
> > +     test_tick &&
> > +     git commit -a -m "test date" \
> > +             --author="Date Author <date@author.example>" \
> > +             --committer="Date Committer <date@committer.example>" \
> > +             --date="2024-06-15 10:30:00 +0800" &&
> > +     git log -1 --format="%ai" >author_date &&
> > +     git log -1 --format="%ci" >committer_date &&
> > +     grep "2024-06-15 10:30:00 +0800" author_date &&
> > +     grep "2024-06-15 10:30:00 +0800" committer_date
> > +'
> > +
> >   test_done
> >
> > base-commit: 4badef0c3503dc29059d678abba7fac0f042bc84
>