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From: Junio C Hamano <gitster@pobox.com>
To: Calvin Wan <calvinwan@google.com>
Cc: git@vger.kernel.org, emilyshaffer@google.com
Subject: Re: [PATCH 3/4] diff-lib: refactor functions
Date: Fri, 23 Sep 2022 13:36:20 -0700	[thread overview]
Message-ID: <xmqqleq9u8u3.fsf@gitster.g> (raw)
In-Reply-To: <20220922232947.631309-4-calvinwan@google.com> (Calvin Wan's message of "Thu, 22 Sep 2022 23:29:46 +0000")

Calvin Wan <calvinwan@google.com> writes:

> Flatten out the if statements in match_stat_with_submodule so the
> logic is more readable and easier for future patches to add to.
>
> Move code that updates relevant variables from the end of
> run_diff_files to finish_run_diff_files. A future patch will utilize
> said function.
>
> Signed-off-by: Calvin Wan <calvinwan@google.com>
> ---
>  diff-lib.c | 71 ++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 42 insertions(+), 29 deletions(-)
>
> diff --git a/diff-lib.c b/diff-lib.c
> index 7eb66a417a..2e148b79e6 100644
> --- a/diff-lib.c
> +++ b/diff-lib.c
> @@ -73,21 +73,50 @@ static int match_stat_with_submodule(struct diff_options *diffopt,
>  				     unsigned *dirty_submodule)
>  {
>  	int changed = ie_match_stat(diffopt->repo->index, ce, st, ce_option);
> -	if (S_ISGITLINK(ce->ce_mode)) {
> -		struct diff_flags orig_flags = diffopt->flags;
> -		if (!diffopt->flags.override_submodule_config)
> -			set_diffopt_flags_from_submodule_config(diffopt, ce->name);
> -		if (diffopt->flags.ignore_submodules)
> -			changed = 0;
> -		else if (!diffopt->flags.ignore_dirty_submodules &&
> -			 (!changed || diffopt->flags.dirty_submodules))
> -			*dirty_submodule = is_submodule_modified(ce->name,
> -								 diffopt->flags.ignore_untracked_in_submodules);
> -		diffopt->flags = orig_flags;
> +	struct diff_flags orig_flags = diffopt->flags;
> +	if (!S_ISGITLINK(ce->ce_mode))
> +		goto cleanup;
> +	if (!diffopt->flags.override_submodule_config)
> +		set_diffopt_flags_from_submodule_config(diffopt, ce->name);
> +	if (diffopt->flags.ignore_submodules) {
> +		changed = 0;
> +		goto cleanup;
>  	}
> +	if (!diffopt->flags.ignore_dirty_submodules &&
> +		(!changed || diffopt->flags.dirty_submodules))
> +			*dirty_submodule = is_submodule_modified(ce->name,
> +							diffopt->flags.ignore_untracked_in_submodules);
> +cleanup:
> +	diffopt->flags = orig_flags;
>  	return changed;
>  }

Unlike the original, this always makes two needless structure
assignments for anything that is not a submodule.  

Can we fix that regression before moving forward?

Even when ce_mode is a gitlink, if .ignore_submodules bit is set,
the two structure assignments between diffopt->flags and orig_flags
become necessary, so the original was already doing extra copies but
we do not have to make it worse.

> +static void finish_run_diff_files(struct rev_info *revs,
> +						  struct cache_entry *ce,
> +						  struct index_state *istate,
> +						  int changed, int dirty_submodule,
> +						  unsigned int newmode)
> +{
> +	unsigned int oldmode;
> +	const struct object_id *old_oid, *new_oid;
> +
> +	if (!changed && !dirty_submodule) {
> +			ce_mark_uptodate(ce);
> +			if (!S_ISGITLINK(ce->ce_mode))
> +				mark_fsmonitor_valid(istate, ce);
> +			if (!revs->diffopt.flags.find_copies_harder)
> +				return;
> +		}
> +		oldmode = ce->ce_mode;
> +		old_oid = &ce->oid;
> +		new_oid = changed ? null_oid() : &ce->oid;
> +		diff_change(&revs->diffopt, oldmode, newmode,
> +			    old_oid, new_oid,
> +			    !is_null_oid(old_oid),
> +			    !is_null_oid(new_oid),
> +			    ce->name, 0, dirty_submodule);
> +}

Strange indentation.  It is unclear why this bottom 1/3 of the loop
body of run_diff_files() need to be a separate helper function,
while the top 2/3 does not.  The resulting loop (below) becomes very
hard to follow because the reader cannot tell when diff_change() is
called and when it is not.

Overall, I see this change detrimental to diff-lib API at this step
in the series.  Later steps may show something more rewarding than
the downsides we see here, hopefully.

  reply	other threads:[~2022-09-23 20:43 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-22 23:29 [PATCH 0/4] submodule: parallelize status Calvin Wan
2022-09-22 23:29 ` [PATCH 1/4] run-command: add pipe_output to run_processes_parallel Calvin Wan
2022-09-23  7:52   ` Ævar Arnfjörð Bjarmason
2022-09-26 16:59     ` Calvin Wan
2022-09-27 10:52       ` Ævar Arnfjörð Bjarmason
2022-09-23 18:58   ` Junio C Hamano
2022-09-26 17:31     ` Calvin Wan
2022-09-27  4:45       ` Junio C Hamano
2022-09-27 18:10         ` Calvin Wan
2022-09-27 21:40           ` Junio C Hamano
2022-09-27  9:05       ` Ævar Arnfjörð Bjarmason
2022-09-27 17:55         ` Calvin Wan
2022-09-27 19:34           ` Ævar Arnfjörð Bjarmason
2022-09-27 20:45             ` Calvin Wan
2022-09-28  5:40               ` Ævar Arnfjörð Bjarmason
2022-09-29 20:52                 ` Calvin Wan
2022-09-22 23:29 ` [PATCH 2/4] submodule: move status parsing into function Calvin Wan
2022-09-22 23:29 ` [PATCH 3/4] diff-lib: refactor functions Calvin Wan
2022-09-23 20:36   ` Junio C Hamano [this message]
2022-09-26 17:35     ` Calvin Wan
2022-09-22 23:29 ` [PATCH 4/4] diff-lib: parallelize run_diff_files for submodules Calvin Wan
2022-09-23  8:06   ` Ævar Arnfjörð Bjarmason
2022-09-24 20:17     ` Junio C Hamano
2022-09-26 17:50     ` Calvin Wan
2022-09-23 21:44   ` Junio C Hamano
2022-09-26 19:12     ` Calvin Wan
2022-09-25 13:59   ` Phillip Wood
2022-09-26 17:11     ` Junio C Hamano
2022-09-26 19:22     ` Calvin Wan
2022-09-27 18:40   ` Emily Shaffer
2022-09-23 22:56 ` [PATCH 0/4] submodule: parallelize status Junio C Hamano
2022-09-26 16:33   ` Calvin Wan

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