[PATCH 05/34] diff.h: drop diff_tree_oid() & friends' return value

["SZEDER Gábor" <szeder.dev@gmail.com>]

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>
---
 diff.h      | 10 +++++-----
 revision.c  |  9 +++------
 tree-diff.c | 21 +++++++++------------
 3 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/diff.h b/diff.h
index 6febe7e365..a1459de824 100644
--- a/diff.h
+++ b/diff.h
@@ -426,11 +426,11 @@ 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;
diff --git a/revision.c b/revision.c
index 8136929e23..9dac1262ef 100644
--- a/revision.c
+++ b/revision.c
@@ -655,15 +655,12 @@ 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);
 	return tree_difference;
 }
 
 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)
@@ -671,9 +668,9 @@ 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 {
diff --git a/tree-diff.c b/tree-diff.c
index 33ded7f8b3..9775e4bcaa 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -29,7 +29,7 @@ static struct combine_diff_path *ll_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);
-static int ll_diff_tree_oid(const struct object_id *old_oid,
+static void ll_diff_tree_oid(const struct object_id *old_oid,
 			    const struct object_id *new_oid,
 			    struct strbuf *base, struct diff_options *opt);
 
@@ -673,7 +673,7 @@ static void try_to_follow_renames(const struct object_id *old_oid,
 	q->nr = 1;
 }
 
-static int ll_diff_tree_oid(const struct object_id *old_oid,
+static void ll_diff_tree_oid(const struct object_id *old_oid,
 			    const struct object_id *new_oid,
 			    struct strbuf *base, struct diff_options *opt)
 {
@@ -691,29 +691,26 @@ static int ll_diff_tree_oid(const struct object_id *old_oid,
 	}
 
 	opt->pathchange = pathchange_old;
-	return 0;
 }
 
-int diff_tree_oid(const struct object_id *old_oid,
-		  const struct object_id *new_oid,
-		  const char *base_str, struct diff_options *opt)
+void diff_tree_oid(const struct object_id *old_oid,
+		   const struct object_id *new_oid,
+		   const char *base_str, struct diff_options *opt)
 {
 	struct strbuf base;
-	int retval;
 
 	strbuf_init(&base, PATH_MAX);
 	strbuf_addstr(&base, base_str);
 
-	retval = ll_diff_tree_oid(old_oid, new_oid, &base, opt);
+	ll_diff_tree_oid(old_oid, new_oid, &base, opt);
 	if (!*base_str && opt->flags.follow_renames && diff_might_be_rename())
 		try_to_follow_renames(old_oid, new_oid, &base, opt);
 
 	strbuf_release(&base);
-
-	return retval;
 }
 
-int diff_root_tree_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)
 {
-	return diff_tree_oid(NULL, new_oid, base, opt);
+	diff_tree_oid(NULL, new_oid, base, opt);
 }
-- 
2.27.0.rc1.431.g5c813f95dc