Re: [PATCH v6 3/4] trailer: append trailers in-process and drop the fork to `interpret-trailers`

Hi Phillip,

 ---- On Tue, 11 Nov 2025 00:38:55 +0800  Phillip Wood <phillip.wood123@gmail.com> wrote --- 
 > Hi Li
 > 
 > On 05/11/2025 14:29, Li Chen wrote:
 > > From: Li Chen <chenl311@chinatelecom.cn>
 > > 
 > > diff --git a/builtin/commit.c b/builtin/commit.c
 > > index 0243f17d53..67070d6a54 100644
 > > --- a/builtin/commit.c
 > > +++ b/builtin/commit.c
 > > @@ -1719,7 +1719,7 @@ int cmd_commit(int argc,
 > >           OPT_STRING(0, "fixup", &fixup_message, N_("[(amend|reword):]commit"), N_("use autosquash formatted message to fixup or amend/reword specified commit")),
 > >           OPT_STRING(0, "squash", &squash_message, N_("commit"), N_("use autosquash formatted message to squash specified commit")),
 > >           OPT_BOOL(0, "reset-author", &renew_authorship, N_("the commit is authored by me now (used with -C/-c/--amend)")),
 > > -        OPT_PASSTHRU_ARGV(0, "trailer", &trailer_args, N_("trailer"), N_("add custom trailer(s)"), PARSE_OPT_NONEG),
 > 
 > We have OPT_STRVEC to handle this. The commit message should explain why 
 > we're doing this (because we only want to pass the value to 
 > amend_file_with_trailers()). Alternatively we could use skip_prefix() in 
 > amend_file_with_trailers() to skip the "--trailer=" prefix in this patch 
 > and then clean it in a separate patch.
 > 
 > > +        OPT_CALLBACK_F(0, "trailer", &trailer_args, N_("trailer"), N_("add custom trailer(s)"), PARSE_OPT_NONEG, parse_opt_strvec),
 > >           OPT_BOOL('s', "signoff", &signoff, N_("add a Signed-off-by trailer")),
 > >           OPT_FILENAME('t', "template", &template_file, N_("use specified template file")),
 > >           OPT_BOOL('e', "edit", &edit_flag, N_("force edit of commit")),
 > > diff --git a/builtin/interpret-trailers.c b/builtin/interpret-trailers.c
 > > index bce2e791d6..268a43372b 100644
 > > --- a/builtin/interpret-trailers.c
 > > +++ b/builtin/interpret-trailers.c
 > > 
 > > @@ -142,21 +110,15 @@ static void interpret_trailers(const struct process_trailer_options *opts,
 > >   {
 > >       struct strbuf sb = STRBUF_INIT;
 > >       struct strbuf out = STRBUF_INIT;
 > > -    FILE *outfile = stdout;
 > > -
 > > -    trailer_config_init();
 > 
 > Why is this being moved?

In v7 I'll initialize trailer config once in cmd_interpret_trailers() (after option parsing), and keep interpret_trailers() focused on read input / call helper / emit output.

 > >       read_input_file(&sb, file);
 > >   
 > > -    if (opts->in_place)
 > > -        outfile = create_in_place_tempfile(file);
 > > -
 > >       process_trailers(opts, new_trailer_head, &sb, &out);
 > >   
 > > -    fwrite(out.buf, out.len, 1, outfile);
 > >       if (opts->in_place)
 > > -        if (rename_tempfile(&trailers_tempfile, file))
 > > -            die_errno(_("could not rename temporary file to %s"), file);
 > > +        write_file_buf(file, out.buf, out.len);
 > 
 > This truncates the existing file which means that if there is a error 
 > while writing the new version the user is now left with garbage rather 
 > than the original file which does not seem like a good idea.

Great catch! v7 will keep --in-place writing via tempfile+rename (no truncate+write), matching the previous behavior.

Regards, Li​