Subject: Re: [PATCH] format-patch: allow a non-integral version numbers

From: Junio C Hamano <[email-masked]>
Date: Thu, 25 Feb 2021 10:13:24 -0800

"ZheNing Hu via GitGitGadget" <[email-masked]> writes:

> From: ZheNing Hu <[email-masked]>
>
> Usually we can only use `format-patch -v<n>` to generate integral
> version numbers patches, but if we can provide `format-patch` with
> non-integer versions numbers of patches, this may help us to send patches
> such as "v1.1" versions sometimes.

A pro-tip.  Do not make your change sound like "because we can do
this"; a change sells a lot easier if it were "because we need
this---see how useful it is in such and such cases".

I am not in principle opposed to support a fractional version number
that comes after an integral one, which allows users to signal that
it is a minor correction that does not deserve a full version bump.

But not in this form.

 - This implementation regresses the output of the diff_version()
   helper function, and does so deliberately, even by butchering a
   test that protects it to hide the regression from the test suite.

   "This is the change from the last version" is expecting too much
   from the reviewers.  Those who may recall seeing your v3 may have
   been otherwise occupied for a few weeks and ununware of your v4.

 - It also closes the door to a feature that is occasionally
   requested to update the make_cover_letter() to carry title and
   description over from the previous iteration.

If we were to do this, I would probably suggest a preliminary patch
that refactors the hardcoded "reroll_count - 1" out of diff_title()
so that the helper takes two "reroll count strings", i.e. reroll
count for this round, and the previous round, as two separate
parameters.  Teach the caller to pass "reroll_count - 1" for the new
parameter in this preliminary step.

Then in the main patch, soon after we finish parsing the command
line options to learn we got "-v$N" argument:

 (0) It might be acceptable to teach the command a new option to
     allow end-users to explicitly give the previous reroll count
     string from the command line.  If we were to do so, skip
     everything below when such an option is used and use the
     user-supplied one.

 (1) If $N is an integer, use $N and $N-1 as the reroll count
     strings for this and previous round.

 (2) Otherwise, scan for "v(.*)-0*-cover-letter.$suffix" in the
     output directory to find all previous rerolls, and pick the one
     that sorts the last and before $N (use versioncmp).  If there
     are existing v1-, v2-, etc., and if we are given "-v2.1" from
     the command line, we'd want to grab v2 as the previous reroll
     count.

 (3) After doing the above steps, if we still do not have the
     previous reroll count string, error out.

     You could argue that we may optionally work in degraded mode,
     using "last version" as the fallback value for the previous
     round count string, and it may work for some things (e.g. the
     "change against the last round" label) and not for other things
     (e.g. reuse description in the previous cover letter).  I would
     not recommend it.

And then, we have two reroll count strings that we can feed
diff_title(); we also can later use the reroll count string for the
previous round to teach make_cover_letter() read and recover the
description from the cover letter of the previous round.

Thanks.

>
> Signed-off-by: ZheNing Hu <[email-masked]>
> ---
>     [GSOC] format-patch: allow a non-integral version numbers
>     
>      * format-patch previously only integer version number -v<n>, now trying
>        to provide a non-integer version.
>     
>     this want to fix #882 Thanks.
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-885%2Fadlternative%2Fformat_patch_non_intergral-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-885/adlternative/format_patch_non_intergral-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/885
>
>  Documentation/git-format-patch.txt |  6 +++---
>  builtin/log.c                      | 20 ++++++++++----------
>  log-tree.c                         |  4 ++--
>  revision.h                         |  2 +-
>  t/t4014-format-patch.sh            |  8 ++++----
>  5 files changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
> index 3e49bf221087..0cc39dbf573c 100644
> --- a/Documentation/git-format-patch.txt
> +++ b/Documentation/git-format-patch.txt
> @@ -215,12 +215,12 @@ populated with placeholder text.
>  
>  -v <n>::
>  --reroll-count=<n>::
> -	Mark the series as the <n>-th iteration of the topic. The
> +	Mark the series as the specified version of the topic. The
>  	output filenames have `v<n>` prepended to them, and the
>  	subject prefix ("PATCH" by default, but configurable via the
>  	`--subject-prefix` option) has ` v<n>` appended to it.  E.g.
> -	`--reroll-count=4` may produce `v4-0001-add-makefile.patch`
> -	file that has "Subject: [PATCH v4 1/20] Add makefile" in it.
> +	`--reroll-count 4.4` may produce `v4.4-0001-add-makefile.patch`
> +	file that has "Subject: [PATCH v4.4 1/20] Add makefile" in it.
>  
>  --to=<email>::
>  	Add a `To:` header to the email headers. This is in addition
> diff --git a/builtin/log.c b/builtin/log.c
> index f67b67d80ed1..72af140b812e 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -1662,13 +1662,13 @@ static void print_bases(struct base_tree_info *bases, FILE *file)
>  	oidclr(&bases->base_commit);
>  }
>  
> -static const char *diff_title(struct strbuf *sb, int reroll_count,
> +static const char *diff_title(struct strbuf *sb, const char *reroll_count,
>  		       const char *generic, const char *rerolled)
>  {
> -	if (reroll_count <= 0)
> +	if (!reroll_count)
>  		strbuf_addstr(sb, generic);
>  	else /* RFC may be v0, so allow -v1 to diff against v0 */
> -		strbuf_addf(sb, rerolled, reroll_count - 1);
> +		strbuf_addf(sb, rerolled, "last version");
>  	return sb->buf;
>  }
>  
> @@ -1717,7 +1717,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  	struct strbuf buf = STRBUF_INIT;
>  	int use_patch_format = 0;
>  	int quiet = 0;
> -	int reroll_count = -1;
> +	const char *reroll_count = NULL;
>  	char *cover_from_description_arg = NULL;
>  	char *branch_name = NULL;
>  	char *base_commit = NULL;
> @@ -1751,8 +1751,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  			    N_("use <sfx> instead of '.patch'")),
>  		OPT_INTEGER(0, "start-number", &start_number,
>  			    N_("start numbering patches at <n> instead of 1")),
> -		OPT_INTEGER('v', "reroll-count", &reroll_count,
> -			    N_("mark the series as Nth re-roll")),
> +		OPT_STRING('v', "reroll-count", &reroll_count, N_("reroll-count"),
> +			    N_("mark the series as specified version re-roll")),
>  		OPT_INTEGER(0, "filename-max-length", &fmt_patch_name_max,
>  			    N_("max length of output filename")),
>  		OPT_CALLBACK_F(0, "rfc", &rev, NULL,
> @@ -1862,9 +1862,9 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  	if (cover_from_description_arg)
>  		cover_from_description_mode = parse_cover_from_description(cover_from_description_arg);
>  
> -	if (0 < reroll_count) {
> +	if (reroll_count) {
>  		struct strbuf sprefix = STRBUF_INIT;
> -		strbuf_addf(&sprefix, "%s v%d",
> +		strbuf_addf(&sprefix, "%s v%s",
>  			    rev.subject_prefix, reroll_count);
>  		rev.reroll_count = reroll_count;
>  		rev.subject_prefix = strbuf_detach(&sprefix, NULL);
> @@ -2080,7 +2080,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  		rev.idiff_oid2 = get_commit_tree_oid(list[0]);
>  		rev.idiff_title = diff_title(&idiff_title, reroll_count,
>  					     _("Interdiff:"),
> -					     _("Interdiff against v%d:"));
> +					     _("Interdiff against %s:"));
>  	}
>  
>  	if (creation_factor < 0)
> @@ -2099,7 +2099,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>  		rev.creation_factor = creation_factor;
>  		rev.rdiff_title = diff_title(&rdiff_title, reroll_count,
>  					     _("Range-diff:"),
> -					     _("Range-diff against v%d:"));
> +					     _("Range-diff against %s:"));
>  	}
>  
>  	if (!signature) {
> diff --git a/log-tree.c b/log-tree.c
> index 4531cebfab38..5f2e08ebcaab 100644
> --- a/log-tree.c
> +++ b/log-tree.c
> @@ -369,8 +369,8 @@ void fmt_output_subject(struct strbuf *filename,
>  	int start_len = filename->len;
>  	int max_len = start_len + info->patch_name_max - (strlen(suffix) + 1);
>  
> -	if (0 < info->reroll_count)
> -		strbuf_addf(filename, "v%d-", info->reroll_count);
> +	if (info->reroll_count)
> +		strbuf_addf(filename, "v%s-", info->reroll_count);
>  	strbuf_addf(filename, "%04d-%s", nr, subject);
>  
>  	if (max_len < filename->len)
> diff --git a/revision.h b/revision.h
> index e6be3c845e66..097d08354c61 100644
> --- a/revision.h
> +++ b/revision.h
> @@ -235,7 +235,7 @@ struct rev_info {
>  	const char	*mime_boundary;
>  	const char	*patch_suffix;
>  	int		numbered_files;
> -	int		reroll_count;
> +	const char	*reroll_count;
>  	char		*message_id;
>  	struct ident_split from_ident;
>  	struct string_list *ref_message_ids;
> diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
> index 66630c8413d5..b911e08f0810 100755
> --- a/t/t4014-format-patch.sh
> +++ b/t/t4014-format-patch.sh
> @@ -372,10 +372,10 @@ test_expect_success 'filename limit applies only to basename' '
>  
>  test_expect_success 'reroll count' '
>  	rm -fr patches &&
> -	git format-patch -o patches --cover-letter --reroll-count 4 main..side >list &&
> -	! grep -v "^patches/v4-000[0-3]-" list &&
> +	git format-patch -o patches --cover-letter --reroll-count 4.4 main..side >list &&
> +	! grep -v "^patches/v4.4-000[0-3]-" list &&
>  	sed -n -e "/^Subject: /p" $(cat list) >subjects &&
> -	! grep -v "^Subject: \[PATCH v4 [0-3]/3\] " subjects
> +	! grep -v "^Subject: \[PATCH v4.4 [0-3]/3\] " subjects
>  '
>  
>  test_expect_success 'reroll count (-v)' '
> @@ -2252,7 +2252,7 @@ test_expect_success 'interdiff: cover-letter' '
>  
>  test_expect_success 'interdiff: reroll-count' '
>  	git format-patch --cover-letter --interdiff=boop~2 -v2 -1 boop &&
> -	test_i18ngrep "^Interdiff ..* v1:$" v2-0000-cover-letter.patch
> +	test_i18ngrep "^Interdiff ..* last version:$" v2-0000-cover-letter.patch
>  '
>  
>  test_expect_success 'interdiff: solo-patch' '
>
> base-commit: 966e671106b2fd38301e7c344c754fd118d0bb07