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

>
> On Sun, Nov 09, 2025 at 10:22:54AM +0000, ZheNing Hu via GitGitGadget wrote:
> > From: ZheNing Hu <adlternative@gmail.com>
> >
> > Add --committer option to git-commit, allowing users to override the
> > committer identity similar to how --author works. This provides a more
> > convenient alternative to setting GIT_COMMITTER_* environment variables.
>
> Yeah, I can see how that's useful.
>

> > 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>...]
>
> Nit: I'd move `--committer` before `--date` so that it comes directly
> after `--author`.
>

> > @@ -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.
>
> This matches the description of `--author`.
>

> > diff --git a/builtin/commit.c b/builtin/commit.c
> > index 0243f17d53..88e77cbaab 100644
> > --- a/builtin/commit.c
> > +++ b/builtin/commit.c
> > @@ -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;
>
> A lot of the infra in this new function is shared with
> `determine_author_info()`. It would be great if we could refactor it so
> that the common parts are shared given that this all is quite
> non-trivial.
>
> Maybe we could have something like `determine_identity()` that contains
> the common bits between both functions? It might ultimately not really
> be worth it, but at least the functionality in the `force_committer`
> condition feels like it should be pulled out.
>

> > @@ -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;
> >
>
> Is it the right thing to search by author here? Shouldn't we rather be
> searching by committer?
>

> > @@ -1930,8 +1978,13 @@ int cmd_commit(int argc,
> >               append_merge_tag_headers(parents, &tail);
> >       }
> >
> > +     if (force_committer) {
> > +             determine_committer_info(&committer_ident);
> > +     }
> > +
>
> Nit: we tend to not use braces around single-line bodies.
>