patchblame: drop unused parameter from maybe_changed_path

> We don't use the "parent" parameter at all (probably because the bloom
> filter for a commit is always defined against a single parent anyway).
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> This is on top of ds/blame-on-bloom, which just made it to next.
>
> I _think_ this is the right solution, but perhaps the function should be
> verifying that we're looking at the right parent?

>
>  blame.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/blame.c b/blame.c
> index 9fbf79e47c..da7e28800e 100644
> --- a/blame.c
> +++ b/blame.c
> @@ -1263,7 +1263,6 @@ struct blame_bloom_data {
>  static int bloom_count_queries = 0;
>  static int bloom_count_no = 0;
>  static int maybe_changed_path(struct repository *r,
> -			      struct commit *parent,
>  			      struct blame_origin *origin,
>  			      struct blame_bloom_data *bd)
>  {
> @@ -1355,8 +1354,7 @@ static struct blame_origin *find_origin(struct repository *r,
>  		if (origin->commit->parents &&
>  		    !oidcmp(&parent->object.oid,
>  			    &origin->commit->parents->item->object.oid))
> -			compute_diff = maybe_changed_path(r, parent,
> -							  origin, bd);
> +			compute_diff = maybe_changed_path(r, origin, bd);
>  
>  		if (compute_diff)
>  			diff_tree_oid(get_commit_tree_oid(parent),

> Jeff King <peff@peff.net> writes:
> 
> > We don't use the "parent" parameter at all (probably because the bloom
> > filter for a commit is always defined against a single parent anyway).
> >
> > Signed-off-by: Jeff King <peff@peff.net>
> > ---
> > This is on top of ds/blame-on-bloom, which just made it to next.
> >
> > I _think_ this is the right solution, but perhaps the function should be
> > verifying that we're looking at the right parent?
> 
> Hmph, "solution" to what problem?  Ah, the fact that parent is an
> unused parameter?

> find_origin() runs a tree-diff over "parent" and "origin->commit",
> with literal pathspec limited to the single path.
> 
> And the Bloom filter addition changed the code so that we first
> consult the filter when "origin->commit"'s first parent *is*
> "parent".  Presumably, by asking maybe_changed_path about "origin",
> as "origin" knows what the commit is (i.e. "origin->commit") and
> what path we are talking about (i.e. "origin->path"), it can answer
> "does origin->commit change origin->path relative to its first
> parent?" and it can do so only for the first parent?
> 
> The way I read bloom.c::get_bloom_filter(), it only computes a
> diff-tree between the given commit and its first parent (or an empty
> tree), so I think the above is correct.

> If the bloom filter also computes against an empty tree for root
> commits (I didn't check, but that would make sense), I think that AND
> could be an OR:
>
>    if (!origin->commit->parents ||
>        !oidcmp(...))
>
> though it probably doesn't matter that much in practice. Root commits
> are rather rare.

>
> BTW, we could also be using oideq() here. I thought coccicheck would
> note this, but it doesn't seem to. I suspect we could also get away with
> a direct pointer comparison of "parent == origin->commit->parents->item"
> due to the way we allocate "struct commit", but I'd rather err on the
> safer and less subtle side. :)