Subject: Re: [PATCH] builtin/tag.c: add --trailer arg

From: Patrick Steinhardt <[email-masked]>
Date: Mon, 29 Apr 2024 08:50:01 +0200

On Mon, Apr 29, 2024 at 04:31:15AM +0000, John Passaro via GitGitGadget wrote:
> From: John Passaro <[email-masked]>
> 
> Teach git-tag to accept --trailer option to add trailers to annotated
> tag messages, like git-commit.
> 
> Signed-off-by: John Passaro <[email-masked]>

This feels like a sensible addition to me indeed, thanks!

[snip]
> diff --git a/builtin/tag.c b/builtin/tag.c
> index 9a33cb50b45..0334a5d15ec 100644
> --- a/builtin/tag.c
> +++ b/builtin/tag.c
> @@ -28,9 +28,11 @@
>  #include "date.h"
>  #include "write-or-die.h"
>  #include "object-file-convert.h"
> +#include "run-command.h"
>  
>  static const char * const git_tag_usage[] = {
>  	N_("git tag [-a | -s | -u <key-id>] [-f] [-m <msg> | -F <file>] [-e]\n"
> +	   "        [(--trailer <token>[(=|:)<value>])...]\n"
>  	   "        <tagname> [<commit> | <object>]"),
>  	N_("git tag -d <tagname>..."),
>  	N_("git tag [-n[<num>]] -l [--contains <commit>] [--no-contains <commit>]\n"
> @@ -290,10 +292,11 @@ static const char message_advice_nested_tag[] =
>  static void create_tag(const struct object_id *object, const char *object_ref,
>  		       const char *tag,
>  		       struct strbuf *buf, struct create_tag_options *opt,
> -		       struct object_id *prev, struct object_id *result, char *path)
> +		       struct object_id *prev, struct object_id *result, struct strvec *trailer_args, char *path)

This line is overly long now, let's break it.

>  {
>  	enum object_type type;
>  	struct strbuf header = STRBUF_INIT;
> +	int should_edit;
>  
>  	type = oid_object_info(the_repository, object, NULL);
>  	if (type <= OBJ_NONE)
> @@ -313,14 +316,18 @@ static void create_tag(const struct object_id *object, const char *object_ref,
>  		    tag,
>  		    git_committer_info(IDENT_STRICT));
>  
> -	if (!opt->message_given || opt->use_editor) {
> +	should_edit = opt->use_editor || !opt->message_given;
> +	if (should_edit || trailer_args->nr) {
>  		int fd;
>  
>  		/* write the template message before editing: */
>  		fd = xopen(path, O_CREAT | O_TRUNC | O_WRONLY, 0600);
>  
> -		if (opt->message_given) {
> +		if (opt->message_given && buf->len) {
>  			write_or_die(fd, buf->buf, buf->len);
> +			if (trailer_args->nr && buf->buf[buf->len-1] != '\n') {
> +				write_or_die(fd, "\n", 1);
> +			}

We avoid braces around single-line statements.

I was also wondering whether we can simplify this to:

    if (opt->message_given && buf->len) {
        strbuf_complete(buf, '\n');
        write_or_die(fd, buf->buf, buf->len);
    }

Or does changing `buf` cause problems for us?

>  			strbuf_reset(buf);
>  		} else if (!is_null_oid(prev)) {
>  			write_tag_body(fd, prev);
> @@ -338,10 +345,31 @@ static void create_tag(const struct object_id *object, const char *object_ref,
>  		}
>  		close(fd);
>  
> -		if (launch_editor(path, buf, NULL)) {
> -			fprintf(stderr,
> -			_("Please supply the message using either -m or -F option.\n"));
> -			exit(1);
> +		if (trailer_args->nr) {
> +			struct child_process run_trailer = CHILD_PROCESS_INIT;
> +
> +			strvec_pushl(&run_trailer.args, "interpret-trailers",
> +				     "--in-place", "--no-divider",
> +				     path, NULL);
> +			strvec_pushv(&run_trailer.args, trailer_args->v);
> +			run_trailer.git_cmd = 1;
> +			if (run_command(&run_trailer))
> +				die(_("unable to pass trailers to --trailers"));
> +		}

This part is copied from `builtin/commit.c`. Would it make sense to move
it into a function `amend_trailers_to_file()` or similar that we add to
our trailer API so that we can avoid the code duplication?

> +		if (should_edit) {
> +			if (launch_editor(path, buf, NULL)) {
> +				fprintf(stderr,
> +				_("Please supply the message using either -m or -F option.\n"));
> +				exit(1);
> +			}

I know you simply re-indented the block here, but let's also fix the
indentation of the second argument to fprintf(3P) while at it.

> +		} else if (trailer_args->nr) {
> +			strbuf_reset(buf);
> +			if (strbuf_read_file(buf, path, 0) < 0) {
> +				fprintf(stderr,
> +						_("Please supply the message using either -m or -F option.\n"));
> +				exit(1);
> +			}
>  		}
>  	}
>  
> @@ -416,6 +444,14 @@ struct msg_arg {
>  	struct strbuf buf;
>  };
>  
> +static int opt_pass_trailer(const struct option *opt, const char *arg, int unset)
> +{
> +	BUG_ON_OPT_NEG(unset);
> +
> +	strvec_pushl(opt->value, "--trailer", arg, NULL);
> +	return 0;
> +}
> +
>  static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
>  {
>  	struct msg_arg *msg = opt->value;
> @@ -463,6 +499,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  	struct ref_sorting *sorting;
>  	struct string_list sorting_options = STRING_LIST_INIT_DUP;
>  	struct ref_format format = REF_FORMAT_INIT;
> +	struct strvec trailer_args = STRVEC_INIT;
>  	int icase = 0;
>  	int edit_flag = 0;
>  	struct option options[] = {
> @@ -479,6 +516,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  		OPT_CALLBACK_F('m', "message", &msg, N_("message"),
>  			       N_("tag message"), PARSE_OPT_NONEG, parse_msg_arg),
>  		OPT_FILENAME('F', "file", &msgfile, N_("read message from file")),
> +		OPT_CALLBACK_F(0, "trailer", &trailer_args, N_("trailer"), N_("add custom trailer(s)"), PARSE_OPT_NONEG, opt_pass_trailer),
>  		OPT_BOOL('e', "edit", &edit_flag, N_("force edit of tag message")),
>  		OPT_BOOL('s', "sign", &opt.sign, N_("annotated and GPG-signed tag")),
>  		OPT_CLEANUP(&cleanup_arg),
> @@ -548,7 +586,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  		opt.sign = 1;
>  		set_signing_key(keyid);
>  	}
> -	create_tag_object = (opt.sign || annotate || msg.given || msgfile);
> +	create_tag_object = (opt.sign || annotate || msg.given || msgfile || edit_flag || trailer_args.nr);
>  
>  	if ((create_tag_object || force) && (cmdmode != 0))
>  		usage_with_options(git_tag_usage, options);
> @@ -635,7 +673,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  	else if (!force)
>  		die(_("tag '%s' already exists"), tag);
>  
> -	opt.message_given = msg.given || msgfile;
> +	opt.message_given = msg.given || (msgfile != NULL);
>  	opt.use_editor = edit_flag;

Besides being not required, this change also violates our coding style
where we don't explicitly check for NULL pointers.

>  	if (!cleanup_arg || !strcmp(cleanup_arg, "strip"))
> @@ -653,7 +691,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  		if (force_sign_annotate && !annotate)
>  			opt.sign = 1;
>  		path = git_pathdup("TAG_EDITMSG");
> -		create_tag(&object, object_ref, tag, &buf, &opt, &prev, &object,
> +		create_tag(&object, object_ref, tag, &buf, &opt, &prev, &object, &trailer_args,
>  			   path);

Nit: let's move `&trailer_args` to the next line to not make it overly
long.

>  	}
>  
> @@ -686,6 +724,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
>  	strbuf_release(&reflog_msg);
>  	strbuf_release(&msg.buf);
>  	strbuf_release(&err);
> +	strvec_clear(&trailer_args);
>  	free(msgfile);
>  	return ret;
>  }
> diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
> index 696866d7794..364db2b4685 100755
> --- a/t/t7004-tag.sh
> +++ b/t/t7004-tag.sh
> @@ -668,6 +668,105 @@ test_expect_success \
>  	test_cmp expect actual
>  '
>  
> +# trailers
> +
> +get_tag_header tag-with-inline-message-and-trailers $commit commit $time >expect
> +cat >>expect <<EOF
> +create tag with trailers
> +
> +my-trailer: here
> +alt-trailer: there
> +EOF

You probably just follow precedent in this file, but our modern coding
style sets up the `expect` file inside of the test body itself. You also
do it like that in other tests, so let's be consistent.

The same comment applies to other tests, as well.

Patrick