Subject: Re: [PATCH v3 4/8] combine-diff: do not pass revs->dense_combined_merges redundantly

From: Jens Lehmann <[email-masked]>
Date: Thu, 11 Sep 2014 21:37:45 +0200

Am 08.09.2014 um 19:29 schrieb Junio C Hamano:
> Thomas Rast <[email-masked]> writes:
>
>> The existing code passed revs->dense_combined_merges along revs itself
>> into the combine-diff functions, which is rather redundant.  Remove
>> the 'dense' argument until much further down the callchain to simplify
>> callers.
>
> It was not apparent that the changes to diff_tree_combined_merge()
> was correct without looking at both of its callsites, but one passes
> the .dense_combined_merges member, and the other in submodules
> always gives true, which you covered here:
>
>> Note that while the caller in submodule.c needs to do extra work now,
>> the next commit will simplify this to a single setting again.
>
>> diff --git a/submodule.c b/submodule.c
>> index c3a61e7..0499de6 100644
>> --- a/submodule.c
>> +++ b/submodule.c
>> @@ -482,10 +482,13 @@ static void find_unpushed_submodule_commits(struct commit *commit,
>>   	struct rev_info rev;
>>
>>   	init_revisions(&rev, NULL);
>> +	rev.ignore_merges = 0;
>> +	rev.combined_merges = 1;
>> +	rev.dense_combined_merges = 1;
>>   	rev.diffopt.output_format |= DIFF_FORMAT_CALLBACK;
>>   	rev.diffopt.format_callback = collect_submodules_from_diff;
>>   	rev.diffopt.format_callback_data = needs_pushing;
>> -	diff_tree_combined_merge(commit, 1, &rev);
>> +	diff_tree_combined_merge(commit, &rev);
>>   }
>
> I briefly wondered if there can be any unwanted side effects in this
> particular codepath that is caused by setting rev.combined_merges
> which was not set in the original code, but seeing that this &rev is
> not used for anything other than diff_tree_combined_merge(), it
> should be OK.
>
> Also I wondered if this is leaking whatever in the &rev structure,
> but in this call I think rev is used only for its embedded diffopt
> in a way that does not leak anything, so it seems to be OK, but I'd
> appreciate if submodule folks can double check.

The only thing the collect_submodules_from_diff() callback does
is to collect the to-be-pushed submodules in the needs_pushing
string_list initialized with STRING_LIST_INIT_DUP which is cleared
at the end of push_unpushed_submodules(), so I think we should be
ok here.