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, 5 insertions, 5 deletions

diff --git a/diff.h b/diff.h
index 9443dc1..e0c0af6 100644
--- a/diff.h
+++ b/diff.h
@@ -431,11 +431,11 @@ struct combine_diff_path *diff_tree_paths(
 	struct combine_diff_path *p, const struct object_id *oid,
 	const struct object_id **parents_oid, int nparent,
 	struct strbuf *base, struct diff_options *opt);
-int diff_tree_oid(const struct object_id *old_oid,
-		  const struct object_id *new_oid,
-		  const char *base, struct diff_options *opt);
-int diff_root_tree_oid(const struct object_id *new_oid, const char *base,
-		       struct diff_options *opt);
+void diff_tree_oid(const struct object_id *old_oid,
+		   const struct object_id *new_oid,
+		   const char *base, struct diff_options *opt);
+void diff_root_tree_oid(const struct object_id *new_oid, const char *base,
+			struct diff_options *opt);
 
 struct combine_diff_path {
 	struct combine_diff_path *next;