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

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 8, 2014, 17:29 UTC
Message-ID: <xmqqvboynhq2.fsf@gitster.dls.corp.google.com>
In-Reply-To: <33951a1d4be8ec15eec569e1a36c0a620b9edaa6.1409860234.git.tr@thomasrast.ch>

Thomas Rast <tr@thomasrast.ch> 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.

Show 17 quoted lines

> 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.

Thanks.