builtin/tag.c: add --trailer option

5th follow-up patch taking welcome feedback from Patrick and JCH. Net new changes include suggested tweaks in documentation, error messaging, code formatting, and patch description.

Since git-tag --list --format="%(trailers)" can interpret trailers from annotated tag messages, it seems natural to support --trailer when writing a new tag message.

git-commit accomplishes this by taking --trailer arguments and passing them to git-interpret-trailer. This patch series refactors that logic and uses it to implement --trailer on git-tag.

John Passaro (3):
builtin/commit: use ARGV macro to collect trailers builtin/commit: refactor --trailer logic builtin/tag: add --trailer option

 Documentation/git-tag.txt |  16 +++++-
 builtin/commit.c          |  20 +------
 builtin/tag.c             |  38 ++++++++++---
 t/t7004-tag.sh            | 114 ++++++++++++++++++++++++++++++++++++++
 trailer.c                 |  12 ++++
 trailer.h                 |   9 +++
 6 files changed, 181 insertions(+), 28 deletions(-)

base-commit: d4cc1ec35f3bcce816b69986ca41943f6ce21377
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1723%2Fjpassaro%2Fjp%2Ftag-trailer-arg-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1723/jpassaro/jp/tag-trailer-arg-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/1723

Range-diff vs v4:

1: ce047c58aa8 ! 1: 85f45a57f35 builtin/commit.c: remove bespoke option callback
@@ Metadata
Author: John Passaro <[email protected]>

## Commit message ##
- builtin/commit.c: remove bespoke option callback
+ builtin/commit: use ARGV macro to collect trailers

- Replace git-commit's bespoke callback for --trailer with the standard
- OPT_PASSTHRU_ARGV macro. The bespoke callback was only adding its values
- to a strvec and sanity-checking that unset is always false; both of
- these are already implemented in the parse-option API.
+ Replace git-commit's callback for --trailer with the standard
+ OPT_PASSTHRU_ARGV macro. The callback only adds its values to a strvec
+ and sanity-checking that unset is always false; both of these are
+ already implemented in the parse-option API.

2: 8f53a54bbfe ! 2: 75bb5cc0e8a builtin/commit.c: refactor --trailer logic
@@ Metadata
Author: John Passaro <[email protected]>

## Commit message ##
- builtin/commit.c: refactor --trailer logic
+ builtin/commit: refactor --trailer logic

git-commit adds user trailers to the commit message by passing its --trailer arguments to a child process running `git-interpret-trailers
@@ trailer.c: void trailer_iterator_release(struct trailer_iterator *iter)
strbuf_release(&iter->key);
}
+
-+int amend_file_with_trailers(const char *path, const struct strvec *trailer_args) { ++int amend_file_with_trailers(const char *path, const struct strvec *trailer_args) ++{
+ struct child_process run_trailer = CHILD_PROCESS_INIT;
+
+ run_trailer.git_cmd = 1;
3: f1d68337eda ! 3: d8b3f6229bc builtin/tag.c: add --trailer option
@@ Metadata
Author: John Passaro <[email protected]>

## Commit message ##
- builtin/tag.c: add --trailer option
+ builtin/tag: add --trailer option

- git-tag currently supports interpreting trailers from an annotated tag
- message, using --list --format="%(trailers)". However, to add a trailer
- to a tag message, you must do so using -F or by editing the message.
+ git-tag supports interpreting trailers from an annotated tag message,
+ using --list --format="%(trailers)". However, the available methods to
+ add a trailer to a tag message (namely -F or --editor) are not as
+ ergonomic.

In a previous patch, we moved git-commit's implementation of its --trailer option to the trailer.h API. Let's use that new function to
@@ Documentation/git-tag.txt: This option is only applicable when listing tags with

+--trailer <token>[(=|:)<value>]::
+ Specify a (<token>, <value>) pair that should be applied as a
-+ trailer. (e.g. `git tag --trailer "Signed-off-by:T A Ger \
-+ <[email protected]>" --trailer "Helped-by:C O Mitter \
-+ <[email protected]>"` will add the "Signed-off-by" trailer
-+ and the "Helped-by" trailer to the tag message.)
++ trailer. (e.g. git tag --trailer "Custom-Key: value"
++ will add a "Custom-Key" trailer to the tag message.)
+ The trailer.* configuration variables
+ (linkgit:git-interpret-trailers[1]) can be used to define if
+ a duplicated trailer is omitted, where in the run of trailers
+ each trailer would appear, and other details.
-+ The trailers can be seen in git tag --list using
++ The trailers can be extracted in git tag --list, using
+ --format="%(trailers)" placeholder.
+
-e::
@@ builtin/tag.c: static void create_tag(const struct object_id *object, const char
+ }
+ } 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);
-+ }
++ if (strbuf_read_file(buf, path, 0) < 0)
++ die_errno(_("failed to read '%s'"), path);
}
}

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