Thread (55 messages) 55 messages, 7 authors, 2021-03-23

Re: [PATCH v8 1/2] [GSOC] commit: add --trailer option

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From: Ævar Arnfjörð Bjarmason <hidden>
Date: 2021-03-16 12:53:40

On Mon, Mar 15 2021, ZheNing Hu via GitGitGadget wrote:
From: ZheNing Hu <redacted>

Historically, Git has supported the 'Signed-off-by' commit trailer
using the '--signoff' and the '-s' option from the command line.
But users may need to provide other trailer information from the
command line such as "Helped-by", "Reported-by", "Mentored-by",

Now implement a new `--trailer <token>[(=|:)<value>]` option to pass
other trailers to `interpret-trailers` and insert them into commit
messages.
I paged through v1-v8, looking mostly good so far. Some comments:
quoted hunk ↗ jump to hunk
Signed-off-by: ZheNing Hu <redacted>
---
 Documentation/git-commit.txt |  9 ++++++++-
 builtin/commit.c             | 23 +++++++++++++++++++++++
 t/t7502-commit-porcelain.sh  | 20 ++++++++++++++++++++
 3 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index 17150fa7eabe..f74d320f0c96 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -14,7 +14,7 @@ SYNOPSIS
 	   [--allow-empty-message] [--no-verify] [-e] [--author=<author>]
 	   [--date=<date>] [--cleanup=<mode>] [--[no-]status]
 	   [-i | -o] [--pathspec-from-file=<file> [--pathspec-file-nul]]
-	   [-S[<keyid>]] [--] [<pathspec>...]
+	   [-S[<keyid>]] [--] [<pathspec>...] [(--trailer <token>[(=|:)<value>])...]
 
 DESCRIPTION
 -----------
@@ -166,6 +166,13 @@ The `-m` option is mutually exclusive with `-c`, `-C`, and `-F`.
 
 include::signoff-option.txt[]
 
+--trailer <token>[(=|:)<value>]::
+	Specify a (<token>, <value>) pair that should be applied as a
+	trailer. (e.g. `git commit --trailer "Signed-off-by:C O Mitter \
+	<committer@example.com>" --trailer "Helped-by:C O Mitter \
+	<committer@example.com>"` will add the "Signed-off-by" trailer
+	and the "Helped-by" trailer in the commit message.)
+	See linkgit:git-interpret-trailers[1] for details.
 -n::
 --no-verify::
 	This option bypasses the pre-commit and commit-msg hooks.
diff --git a/builtin/commit.c b/builtin/commit.c
index 739110c5a7f6..250e93d977df 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -113,6 +113,7 @@ static int config_commit_verbose = -1; /* unspecified */
 static int no_post_rewrite, allow_empty_message, pathspec_file_nul;
 static char *untracked_files_arg, *force_date, *ignore_submodule_arg, *ignored_arg;
 static char *sign_commit, *pathspec_from_file;
+static struct strvec trailer_args = STRVEC_INIT;
 
 /*
  * The default commit message cleanup mode will remove the lines
@@ -131,6 +132,14 @@ static struct strbuf message = STRBUF_INIT;
 
 static enum wt_status_format status_format = STATUS_FORMAT_UNSPECIFIED;
 
+static int opt_pass_trailer(const struct option *opt, const char *arg, int unset)
+{
+	BUG_ON_OPT_NEG(unset);
+
+	strvec_pushl(&trailer_args, "--trailer", arg, NULL);
+	return 0;
+}
+
 static int opt_parse_porcelain(const struct option *opt, const char *arg, int unset)
 {
 	enum wt_status_format *value = (enum wt_status_format *)opt->value;
@@ -958,6 +967,19 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 
 	fclose(s->fp);
 
+	if (trailer_args.nr) {
+		struct child_process run_trailer = CHILD_PROCESS_INIT;
+
+		strvec_pushl(&run_trailer.args, "interpret-trailers",
+			     "--in-place", "--if-exists=add",
+			     git_path_commit_editmsg(), NULL);
+		strvec_pushv(&run_trailer.args, trailer_args.v);
+		run_trailer.git_cmd = 1;
+		if (run_command(&run_trailer))
+			strvec_clear(&run_trailer.args);
This is git-commit, shouldn't we die() here instead of ignoring errors
in sub-processes?
quoted hunk ↗ jump to hunk
+		strvec_clear(&trailer_args);
+	}
+
 	/*
 	 * Reject an attempt to record a non-merge empty commit without
 	 * explicit --allow-empty. In the cherry-pick case, it may be
@@ -1507,6 +1529,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		OPT_STRING(0, "fixup", &fixup_message, N_("commit"), N_("use autosquash formatted message to fixup 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_CALLBACK_F(0, "trailer", NULL, N_("trailer"), N_("trailer(s) to add"), PARSE_OPT_NONEG, opt_pass_trailer),
 		OPT_BOOL('s', "signoff", &signoff, N_("add a Signed-off-by trailer")),
Not required for this change, but perhaps a change here to N_() (if we
can get it to fit) + doc update saying that we prefer
--trailer="Signed-Off-By: to --signoff"? More on that later.
quoted hunk ↗ jump to hunk
 		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/t/t7502-commit-porcelain.sh b/t/t7502-commit-porcelain.sh
index 6396897cc818..0acf23799931 100755
--- a/t/t7502-commit-porcelain.sh
+++ b/t/t7502-commit-porcelain.sh
@@ -154,6 +154,26 @@ test_expect_success 'sign off' '
 
 '
 
+test_expect_success 'trailer' '
+	>file1 &&
+	git add file1 &&
+	git commit -s --trailer "Signed-off-by:C O Mitter1 <committer1@example.com>" \
+		--trailer "Helped-by:C O Mitter2 <committer2@example.com>"  \
+		--trailer "Reported-by:C O Mitter3 <committer3@example.com>" \
+		--trailer "Mentored-by:C O Mitter4 <committer4@example.com>" \
+		-m "hello" &&
+	git cat-file commit HEAD >commit.msg &&
+	sed -e "1,7d" commit.msg >actual &&
+	cat >expected <<-\EOF &&
+	Signed-off-by: C O Mitter <committer@example.com>
+	Signed-off-by: C O Mitter1 <committer1@example.com>
+	Helped-by: C O Mitter2 <committer2@example.com>
+	Reported-by: C O Mitter3 <committer3@example.com>
+	Mentored-by: C O Mitter4 <committer4@example.com>
+	EOF
+	test_cmp expected actual
+'
+
How does this interact with cases where the user has configured
"trailer.separators" to have a value that doesn't contain ":"?  I
haven't tested, but my reading of git-interpret-trailers(1) is that if
you supplied "=" instead that case would just work:

    By default only : is recognized as a trailer separator, except that
    = is always accepted on the command line for compatibility with
    other git commands.

I don't know if that does the right thing in the presence of
--if-exists=add.

So it would be good to update these tests so you test:

 * For the --if-exists=add case at all, there's no tests for it
   now. I.e. add some trailers manually to the commit (via -F or
   whatever) and then see if they get added to, replacet etc.

 * Ditto but for the user having configured trailer.separators (see the
   test_config helper for how to set config in a test). I.e. if it's "="
   does adding trailers work, how about if it's "=" on the CLI but the
   config/commit message has ";" instead of ":" or something?

 * Hrm, actually I think tweaking "-c trailer.ifexists" won't work at
   all, since the CLI switch would override it. I honestly don't know,
   but why not not supply it and keep the addIfDifferentNeighbor
   default?

   If it's essential that seems like a good test / documentation
   addition...

 * For the above -c ... case I can't think of a good way to deal with it
   that doesn't involve pulling in git_trailer_config() into
   git_commit_config(), but perhaps the least nasty way is to just set a
   flag in git_commit_config() if we see a "trailer.ifexists" flag, and
   if so don't provide "--if-exists=add", if there's no config (this
   will include "git -c ... commit" we set provide "--if-exists=add" )
   or as noted above, maybe we can skip the whole thing and use the
   addIfDifferentNeighbor default.

And, not needed for this patch but worth thinking about:

 * We pass through --trailer to git-interpret-trailers, what should we
   do about the other options? Should git-commit eventually support
   --trailer-where and pass it along as --where to
   git-interpret-trailers, or is "git -c trailer.where=... commit" good
   enough?

 * It would be good to test for and document if that "-c trailer.*"
   trick works (no reason it shouldn't). I.e. to add something like this
   after what you have (along with tests, and check if it's even true):

       Only the `--trailer` argument to
       linkgit:git-interpret-trailers[1] is supported. Other
       pass-through switches may be added in the future, but currently
       you'll need to pass arguments to
       linkgit:git-interpret-trailers[1] along as config, e.g. `git -c
       trailer.where=start commit [...] --trailer=[...]`.
      
 * We have a longer-term goal of having the .mailmap apply to trailers,
   it would be nice if git-interpret-trailers had some fuzzy-matching to
   check if the RHS of a trailer is a name/E-Mail pair, and if so did
   stricter validation on it with the ident functions we use for fsck
   etc. (that's copied & subtly different in several different places in
   the codebase, unfortunately[1]).

More thoughts:

 * Having written all the above I checked how --signoff is implemented.

   It seems to me to be a good idea to (at least for testing) convert
   the --signoff trailer to your implementation. We have plenty of tests
   for it, does migrating it over pass or fail those?

 * I also agree with Junio that we shouldn't have a --fixed-by or
   whatever and wouldn't add --signoff today, but it seems very useful
   to me to have a shortcut like:

       --trailer "Signed-off-by"

   I.e. omitting the value, or:

      --trailer "Signed-off-by="

   Or some other thing we deem sufficiently useful/sane
   syntax/unambiguous.n

   Then the value would be provided by fmt_name(WANT_COMMITTER_IDENT)
   just as we do in append_signoff() now. I think a *very common* case
   for this would be something like:

       git commit --amend -v --trailer "Reviewed-by"

   And it would be useful to help that along and not have to do:

       git commit --amend -v --trailer "Reviewed-by=$(git config user.name) <$(git config user.email)>"

   Or worse yet, manually typo your name/e-mail address, as I'm sure I
   and many others will inevitably do when using this option...

1. https://lore.kernel.org/git/87bld8ov9q.fsf@evledraar.gmail.com/ (local)
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