Subject: Re: [PATCH 2/2] format-patch: allow for independent diff & range-diff options

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 29 Nov 2018 15:35:24 +0100

On Thu, Nov 29 2018, Johannes Schindelin wrote:

> Hi Ævar,
>
> On Thu, 29 Nov 2018, Ævar Arnfjörð Bjarmason wrote:
>
>> On Thu, Nov 29 2018, Johannes Schindelin wrote:
>>
>> > On Wed, 28 Nov 2018, Ævar Arnfjörð Bjarmason wrote:
>> >
>> >> Change the semantics of the "--range-diff" option so that the regular
>> >> diff options can be provided separately for the range-diff and the
>> >> patch. This allows for supplying e.g. --range-diff-U0 and -U1 to
>> >> "format-patch" to provide different context for the range-diff and the
>> >> patch. This wasn't possible before.
>> >
>> > I really, really dislike the `--range-diff-<random-thing>`. We have
>> > precedent for passing optional arguments that are passed to some other
>> > command, so a much more logical and consistent convention would be to use
>> > `--range-diff[=<diff-option>..]`, allowing all of the diff options that
>> > you might want to pass to the outer diff in one go rather than having a
>> > lengthy string of `--range-diff-this` and `--range-diff-that` options.
>>
>> Where do we pass those sorts of arguments?
>>
>> Reasons I did it this way:
>>
>>  a) Passing it as one option will require the user to double-quote those
>>     options that take quoted arguments (e.g. --word-diff-regex), which I
>>     thought sucked more than the prefix. On the implementation side we
>>     couldn't leave the parsing of the command-line to the shell anymore.
>>
>>  b) I think people will want to tweak this very rarely, much more rarely
>>     than e.g. -U10 in format-patch itself, so having something long-ish
>>     doesn't sound bad.
>
> Hmm. I still don't like it. It sets a precedent, and we simply do not do
> it that way in other circumstances (most obvious would be the -X merge
> options). The more divergent user interfaces for the same sort of thing
> are, the more brain cycles you force users to spend on navigating said
> interfaces.

Yeah it sucks, I just think it sucks less than the alternative :)
I.e. I'm not picky about --range-diff-* prefix the name, but I think
doing our own shell parsing would be nasty.

>> > I only had time to skim the patch, and I have to wonder why you pass
>> > around full-blown `rev_info` structs for range diff (and with that really
>> > awful name `rd_rev`) rather than just the `diff_options` that you
>> > *actually* care about?
>>
>> Because setup_revisions() which does all the command-line parsing needs
>> a rev_info, so even if we only need the diffopt in the end we need to
>> initiate the whole thing.
>>
>> Suggestions for a better varibale name most welcome.
>
> `range_diff_revs`
>
> And you do not need to pass around the whole thing. You can easily pass
> `&range_diff_revs.diffopt`.
>
> Don't pass around what you do not need to pass around.

Ah, you mean internally in log.c, yes that makes sense. I thought you
meant just pass diffopt to setup_revisions() (which needs the containing
struct). Willdo.

> Ciao,
> Dscho
>
>>
>> > Ciao,
>> > Dscho
>> >
>> >>
>> >> Ever since the "--range-diff" option was added in
>> >> 31e2617a5f ("format-patch: add --range-diff option to embed diff in
>> >> cover letter", 2018-07-22) the "rev->diffopt" we pass down to the diff
>> >> machinery has been the one we get from "format-patch"'s own
>> >> setup_revisions().
>> >>
>> >> This sort of thing is unique among the log-like commands in
>> >> builtin/log.c, no command than format-patch will embed the output of
>> >> another log-like command. Since the "rev->diffopt" is reused we need
>> >> to munge it before we pass it to show_range_diff(). See
>> >> 43dafc4172 ("format-patch: don't include --stat with --range-diff
>> >> output", 2018-11-22) for a related regression fix which is being
>> >> mostly reverted here.
>> >>
>> >> Implementation notes: 1) We're not bothering with the full teardown
>> >> around die() and will leak memory, but it's too much boilerplate to do
>> >> all the frees with/without the die() and not worth it. 2) We call
>> >> repo_init_revisions() for "rd_rev" even though we could get away with
>> >> a shallow copy like the code we're replacing (and which
>> >> show_range_diff() itself does). This is to make this code more easily
>> >> understood.
>> >>
>> >> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
>> >> ---
>> >>  Documentation/git-format-patch.txt | 10 ++++++-
>> >>  builtin/log.c                      | 42 +++++++++++++++++++++++-------
>> >>  t/t3206-range-diff.sh              | 41 +++++++++++++++++++++++++++++
>> >>  3 files changed, 82 insertions(+), 11 deletions(-)
>> >>
>> >> diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
>> >> index aba4c5febe..6c048f415f 100644
>> >> --- a/Documentation/git-format-patch.txt
>> >> +++ b/Documentation/git-format-patch.txt
>> >> @@ -24,7 +24,8 @@ SYNOPSIS
>> >>  		   [--to=<email>] [--cc=<email>]
>> >>  		   [--[no-]cover-letter] [--quiet] [--notes[=<ref>]]
>> >>  		   [--interdiff=<previous>]
>> >> -		   [--range-diff=<previous> [--creation-factor=<percent>]]
>> >> +		   [--range-diff=<previous> [--creation-factor=<percent>]
>> >> +		      [--range-diff<common diff option>]]
>> >>  		   [--progress]
>> >>  		   [<common diff options>]
>> >>  		   [ <since> | <revision range> ]
>> >> @@ -257,6 +258,13 @@ feeding the result to `git send-email`.
>> >>  	creation/deletion cost fudge factor. See linkgit:git-range-diff[1])
>> >>  	for details.
>> >>
>> >> +--range-diff<common diff option>::
>> >> +	Other options prefixed with `--range-diff` are stripped of
>> >> +	that prefix and passed as-is to the diff machinery used to
>> >> +	generate the range-diff, e.g. `--range-diff-U0` and
>> >> +	`--range-diff--no-color`. This allows for adjusting the format
>> >> +	of the range-diff independently from the patch itself.
>> >> +
>> >>  --notes[=<ref>]::
>> >>  	Append the notes (see linkgit:git-notes[1]) for the commit
>> >>  	after the three-dash line.
>> >> diff --git a/builtin/log.c b/builtin/log.c
>> >> index 02d88fa233..7658e56ecc 100644
>> >> --- a/builtin/log.c
>> >> +++ b/builtin/log.c
>> >> @@ -1023,7 +1023,8 @@ static void show_diffstat(struct rev_info *rev,
>> >>  	fprintf(rev->diffopt.file, "\n");
>> >>  }
>> >>
>> >> -static void make_cover_letter(struct rev_info *rev, int use_stdout,
>> >> +static void make_cover_letter(struct rev_info *rev, struct rev_info *rd_rev,
>> >> +			      int use_stdout,
>> >>  			      struct commit *origin,
>> >>  			      int nr, struct commit **list,
>> >>  			      const char *branch_name,
>> >> @@ -1095,13 +1096,9 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
>> >>  	}
>> >>
>> >>  	if (rev->rdiff1) {
>> >> -		struct diff_options opts;
>> >> -		memcpy(&opts, &rev->diffopt, sizeof(opts));
>> >> -		opts.output_format &= ~(DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_SUMMARY);
>> >> -
>> >>  		fprintf_ln(rev->diffopt.file, "%s", rev->rdiff_title);
>> >>  		show_range_diff(rev->rdiff1, rev->rdiff2,
>> >> -				rev->creation_factor, 1, &opts);
>> >> +				rev->creation_factor, 1, &rd_rev->diffopt);
>> >>  	}
>> >>  }
>> >>
>> >> @@ -1485,6 +1482,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>> >>  	struct commit *commit;
>> >>  	struct commit **list = NULL;
>> >>  	struct rev_info rev;
>> >> +	struct rev_info rd_rev;
>> >>  	struct setup_revision_opt s_r_opt;
>> >>  	int nr = 0, total, i;
>> >>  	int use_stdout = 0;
>> >> @@ -1603,6 +1601,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>> >>  	init_log_defaults();
>> >>  	git_config(git_format_config, NULL);
>> >>  	repo_init_revisions(the_repository, &rev, prefix);
>> >> +	repo_init_revisions(the_repository, &rd_rev, prefix);
>> >>  	rev.commit_format = CMIT_FMT_EMAIL;
>> >>  	rev.expand_tabs_in_log_default = 0;
>> >>  	rev.verbose_header = 1;
>> >> @@ -1689,8 +1688,32 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>> >>  	rev.preserve_subject = keep_subject;
>> >>
>> >>  	argc = setup_revisions(argc, argv, &rev, &s_r_opt);
>> >> -	if (argc > 1)
>> >> -		die(_("unrecognized argument: %s"), argv[1]);
>> >> +	if (argc > 1) {
>> >> +		struct argv_array args = ARGV_ARRAY_INIT;
>> >> +		const char *prefix = "--range-diff";
>> >> +		int have_prefix = 0;
>> >> +
>> >> +		for (i = 0; i < argc; i++) {
>> >> +			struct strbuf sb = STRBUF_INIT;
>> >> +			char *str;
>> >> +
>> >> +			strbuf_addstr(&sb, argv[i]);
>> >> +			if (starts_with(argv[i], prefix)) {
>> >> +				have_prefix = 1;
>> >> +				strbuf_remove(&sb, 0, strlen(prefix));
>> >> +			}
>> >> +			str = strbuf_detach(&sb, NULL);
>> >> +			strbuf_release(&sb);
>> >> +
>> >> +			argv_array_push(&args, str);
>> >> +		}
>> >> +
>> >> +		if (!have_prefix)
>> >> +			die(_("unrecognized argument: %s"), argv[1]);
>> >> +		argc = setup_revisions(args.argc, args.argv, &rd_rev, NULL);
>> >> +		if (argc > 1)
>> >> +			die(_("unrecognized argument: %s"), argv[1]);
>> >> +	}
>> >>
>> >>  	if (rev.diffopt.output_format & DIFF_FORMAT_NAME)
>> >>  		die(_("--name-only does not make sense"));
>> >> @@ -1702,7 +1725,6 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>> >>  	if (!use_patch_format &&
>> >>  		(!rev.diffopt.output_format ||
>> >>  		 rev.diffopt.output_format == DIFF_FORMAT_PATCH))
>> >> -		/* Needs to be mirrored in show_range_diff() invocation */
>> >>  		rev.diffopt.output_format = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_SUMMARY;
>> >>  	if (!rev.diffopt.stat_width)
>> >>  		rev.diffopt.stat_width = MAIL_DEFAULT_WRAP;
>> >> @@ -1877,7 +1899,7 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
>> >>  	if (cover_letter) {
>> >>  		if (thread)
>> >>  			gen_message_id(&rev, "cover");
>> >> -		make_cover_letter(&rev, use_stdout,
>> >> +		make_cover_letter(&rev, &rd_rev, use_stdout,
>> >>  				  origin, nr, list, branch_name, quiet);
>> >>  		print_bases(&bases, rev.diffopt.file);
>> >>  		print_signature(rev.diffopt.file);
>> >> diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
>> >> index bc5facc1cd..6916103888 100755
>> >> --- a/t/t3206-range-diff.sh
>> >> +++ b/t/t3206-range-diff.sh
>> >> @@ -308,6 +308,35 @@ test_expect_success 'format-patch with <common diff option>' '
>> >>  		--range-diff=topic~..topic changed~..changed >actual.raw &&
>> >>  	sed -ne "/^1:/,/^--/p" <actual.raw >actual.range-diff &&
>> >>  	sed -e "s|:$||" >expect <<-\EOF &&
>> >> +	1:  a63e992 ! 1:  d966c5c s/12/B/
>> >> +	    @@ -8,7 +8,7 @@
>> >> +	     @@
>> >> +	      9
>> >> +	      10
>> >> +	    - B
>> >> +	    + BB
>> >> +	     -12
>> >> +	     +B
>> >> +	      13
>> >> +	-- :
>> >> +	EOF
>> >> +	test_cmp expect actual.range-diff &&
>> >> +	sed -ne "/^--- /,/^--/p" <actual.raw >actual.diff &&
>> >> +	sed -e "s|:$||" >expect <<-\EOF &&
>> >> +	--- a/file
>> >> +	+++ b/file
>> >> +	@@ -12 +12 @@ BB
>> >> +	-12
>> >> +	+B
>> >> +	-- :
>> >> +	EOF
>> >> +	test_cmp expect actual.diff &&
>> >> +
>> >> +	# -U0 & --range-diff-U0
>> >> +	git format-patch --cover-letter --stdout -U0 --range-diff-U0 \
>> >> +		--range-diff=topic~..topic changed~..changed >actual.raw &&
>> >> +	sed -ne "/^1:/,/^--/p" <actual.raw >actual.range-diff &&
>> >> +	sed -e "s|:$||" >expect <<-\EOF &&
>> >>  	1:  a63e992 ! 1:  d966c5c s/12/B/
>> >>  	    @@ -11 +11 @@
>> >>  	    - B
>> >> @@ -327,4 +356,16 @@ test_expect_success 'format-patch with <common diff option>' '
>> >>  	test_cmp expect actual.diff
>> >>  '
>> >>
>> >> +test_expect_success 'format-patch option parsing with --range-diff-*' '
>> >> +	test_must_fail git format-patch --stdout --unknown \
>> >> +		master..unmodified 2>stderr &&
>> >> +	test_i18ngrep "unrecognized argument: --unknown" stderr &&
>> >> +	test_must_fail git format-patch --stdout --range-diff-unknown \
>> >> +		master..unmodified 2>stderr &&
>> >> +	test_i18ngrep "unrecognized argument: --range-diff-unknown" stderr &&
>> >> +	test_must_fail git format-patch --stdout --unknown --range-diff-unknown \
>> >> +		master..unmodified 2>stderr &&
>> >> +	test_i18ngrep "unrecognized argument: --unknown" stderr
>> >> +'
>> >> +
>> >>  test_done
>> >> --
>> >> 2.20.0.rc1.387.gf8505762e3
>> >>
>> >>
>>