Re: [PATCH v2 3/7] log: do not free parents when walking reflog

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 9, 2017, 16:59 UTC
Message-ID: <xmqqtw2l8s22.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170709101351.qcwgtzly72wwvwmq@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 25 quoted lines

> On Fri, Jul 07, 2017 at 10:10:54AM -0700, Junio C Hamano wrote:
>
>> > diff --git a/builtin/log.c b/builtin/log.c
>> > index 8ca1de9894..9c8bb3b5c3 100644
>> > --- a/builtin/log.c
>> > +++ b/builtin/log.c
>> > @@ -374,9 +374,9 @@ static int cmd_log_walk(struct rev_info *rev)
>> >  		if (!rev->reflog_info) {
>> >  			/* we allow cycles in reflog ancestry */
>> >  			free_commit_buffer(commit);
>> > +			free_commit_list(commit->parents);
>> > +			commit->parents = NULL;
>> 
>> After step 6/7, we no longer "allow cycles in reflog ancestry", as
>> there will be no reflog ancestry to speak of ;-), so it would be
>> nice to remove the comment above in that step.  But alternatively,
>> we can rephrase the comment here, to say something like "the same
>> commit can be shown multiple times while showing entries from the
>> reflog" instead.
>
> I actually think the comment is a bit obtuse in the first place. The
> real issue is that we show commits multiple times. That's caused by
> cycles, yes, but also by us clearing the SEEN flag. ;)
>
> Maybe this on top?

Yup, that is a much better version of what I had in mind that can go either before this step as a preparatory cleanup, squashed into this as "while at it", or after the series as a finishing touches. The last one will let the codebase lie for a short while, though, so I am likely to squash it in or wiggle it under.

Thanks.

Show 32 quoted lines

>
> -- >8 --
> Subject: [PATCH] log: clarify comment about reflog cycles
>
> When we're walking reflogs, we leave the commit buffer and
> parents in place. A comment explains that this is due to
> "cycles". But the interesting thing is the unsaid
> implication: that the cycles (plus our clearing of the SEEN
> flag) will cause us to show commits multiple times. Let's
> spell it out.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  builtin/log.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/builtin/log.c b/builtin/log.c
> index 9c8bb3b5c..630d6cff2 100644
> --- a/builtin/log.c
> +++ b/builtin/log.c
> @@ -372,7 +372,10 @@ static int cmd_log_walk(struct rev_info *rev)
>  			 */
>  			rev->max_count++;
>  		if (!rev->reflog_info) {
> -			/* we allow cycles in reflog ancestry */
> +			/*
> +			 * We may show a given commit multiple times when
> +			 * walking the reflogs.
> +			 */
>  			free_commit_buffer(commit);
>  			free_commit_list(commit->parents);
>  			commit->parents = NULL;