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

From: Junio C Hamano <[email-masked]>
Date: Mon, 08 Sep 2014 10:29:41 -0700

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.

Thanks.