Stabilize order for equiv tree iterator entries

Given a group of case-insensitively equivalent tree iterator
entries, this ensures that the case-sensitively first trees will
be used as the representative items.  I.e. if you have conflicting
entries "A/B/x", "a/b/x", and "A/b/x", this change ensures that
the earliest entry "A/B/x" will be returned.  The actual choice
is not that important, but it is nice to have it stable and to
have it been either the first or last item, as opposed to a
random item from within the equivalent span.

1 files changed, 15 insertions, 3 deletions

diff --git a/src/iterator.c b/src/iterator.c
index fb76085cd..e6e0ea481 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -285,9 +285,21 @@ static int tree_iterator__tree_entry_cmp(
 
 static int tree_iterator__entry_cmp(const void *a, const void *b, void *p)
 {
-	return tree_iterator__tree_entry_cmp(
-		tree_iterator__tree_entry(p, a), tree_iterator__tree_entry(p, b),
-		git__strncasecmp);
+	const tree_iterator_entry *ae = a, *be = b;
+	const git_tree_entry *ate = tree_iterator__tree_entry(p, ae);
+	const git_tree_entry *bte = tree_iterator__tree_entry(p, be);
+	int cmp = tree_iterator__tree_entry_cmp(ate, bte, git__strncasecmp);
+
+	/* stabilize sort order among equivalent names */
+	if (!cmp) {
+		cmp = (ae->parent_entry_index < be->parent_entry_index) ? -1 :
+			(ae->parent_entry_index > be->parent_entry_index) ? 1 : 0;
+		if (!cmp)
+			cmp = (ae->parent_tree_index < be->parent_tree_index) ? -1 :
+				(ae->parent_tree_index > be->parent_tree_index) ? 1 : 0;
+	}
+
+	return cmp;
 }
 
 static int tree_iterator__set_next(tree_iterator *ti, tree_iterator_frame *tf)