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 11:30:22 +0100

On Thu, Nov 29 2018, Johannes Schindelin wrote:

> Hi Ævar,
>
> 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.

> 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.

> 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
>>
>>