unpack_callback(): use unpack_failed() consistently

When unpack_index_entry() failed, consistently call unpack_failed(),
instead of silently returning -1.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

unpack-trees.c

@@ -277,6 +277,17 @@ static int unpack_nondirectories(int n, unsigned long mask,
 	return 0;
 }
 
+static int unpack_failed(struct unpack_trees_options *o, const char *message)
+{
+	discard_index(&o->result);
+	if (!o->gently) {
+		if (message)
+			return error("%s", message);
+		return -1;
+	}
+	return -1;
+}
+
 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
 {
 	struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
@@ -294,7 +305,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 			int cmp = compare_entry(ce, info, p);
 			if (cmp < 0) {
 				if (unpack_index_entry(ce, o) < 0)
-					return -1;
+					return unpack_failed(o, NULL);
 				continue;
 			}
 			if (!cmp) {
@@ -352,17 +363,6 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 	return mask;
 }
 
-static int unpack_failed(struct unpack_trees_options *o, const char *message)
-{
-	discard_index(&o->result);
-	if (!o->gently) {
-		if (message)
-			return error("%s", message);
-		return -1;
-	}
-	return -1;
-}
-
 /*
  * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
  * resulting index, -2 on failure to reflect the changes to the work tree.