diff.h: drop diff_tree_oid() & friends' return value

ll_diff_tree_oid() has only ever returned 0 [1], so it's return value
is basically useless.  It's only caller diff_tree_oid() has only ever
returned the return value of ll_diff_tree_oid() as-is [2], so its
return value is just as useless.  Most of diff_tree_oid()'s callers
simply ignore its return value, except:

  - diff_root_tree_oid() is a thin wrapper around diff_tree_oid() and
    returns with its return value, but all of diff_root_tree_oid()'s
    callers ignore its return value.

  - rev_compare_tree() and rev_same_tree_as_empty() do look at the
    return value in a condition, but, since the return value is always
    0, the former's < 0 condition is never fulfilled, while the
    latter's >= 0 condition is always fulfilled.

So let's drop the return value of ll_diff_tree_oid(), diff_tree_oid()
and diff_root_tree_oid(), and drop those conditions from
rev_compare_tree() and rev_same_tree_as_empty() as well.

[1] ll_diff_tree_oid() and its ancestors have been returning only 0
    ever since it was introduced as diff_tree() in 9174026cfe (Add
    "diff-tree" program to show which files have changed between two
    trees., 2005-04-09).
[2] diff_tree_oid() traces back to diff-tree.c:main() in 9174026cfe as
    well.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 6 deletions

diff --git a/revision.c b/revision.c
index cbf4b61..c644c66 100644
--- a/revision.c
+++ b/revision.c
@@ -791,9 +791,7 @@ static int rev_compare_tree(struct rev_info *revs,
 
 	tree_difference = REV_TREE_SAME;
 	revs->pruning.flags.has_changes = 0;
-	if (diff_tree_oid(&t1->object.oid, &t2->object.oid, "",
-			   &revs->pruning) < 0)
-		return REV_TREE_DIFFERENT;
+	diff_tree_oid(&t1->object.oid, &t2->object.oid, "", &revs->pruning);
 
 	if (!nth_parent)
 		if (bloom_ret == 1 && tree_difference == REV_TREE_SAME)
@@ -804,7 +802,6 @@ static int rev_compare_tree(struct rev_info *revs,
 
 static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 {
-	int retval;
 	struct tree *t1 = get_commit_tree(commit);
 
 	if (!t1)
@@ -812,9 +809,9 @@ static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 
 	tree_difference = REV_TREE_SAME;
 	revs->pruning.flags.has_changes = 0;
-	retval = diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
+	diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
 
-	return retval >= 0 && (tree_difference == REV_TREE_SAME);
+	return tree_difference == REV_TREE_SAME;
 }
 
 struct treesame_state {