commit: move reverse_commit_list() from merge-recursive

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.c

@@ -563,6 +563,17 @@ struct commit_list *copy_commit_list(struct commit_list *list)
 	return head;
 }
 
+struct commit_list *reverse_commit_list(struct commit_list *list)
+{
+	struct commit_list *next = NULL, *current, *backup;
+	for (current = list; current; current = backup) {
+		backup = current->next;
+		current->next = next;
+		next = current;
+	}
+	return next;
+}
+
 void free_commit_list(struct commit_list *list)
 {
 	while (list)

commit.h

@@ -177,6 +177,9 @@ void commit_list_sort_by_date(struct commit_list **list);
 /* Shallow copy of the input list */
 struct commit_list *copy_commit_list(struct commit_list *list);
 
+/* Modify list in-place to reverse it, returning new head; list will be tail */
+struct commit_list *reverse_commit_list(struct commit_list *list);
+
 void free_commit_list(struct commit_list *list);
 
 struct rev_info; /* in revision.h, it circularly uses enum cmit_fmt */

merge-recursive.c

@@ -3517,17 +3517,6 @@ static int merge_trees_internal(struct merge_options *opt,
 	return clean;
 }
 
-static struct commit_list *reverse_commit_list(struct commit_list *list)
-{
-	struct commit_list *next = NULL, *current, *backup;
-	for (current = list; current; current = backup) {
-		backup = current->next;
-		current->next = next;
-		next = current;
-	}
-	return next;
-}
-
 /*
  * Merge the commits h1 and h2, returning a flag (int) indicating the
  * cleanness of the merge.  Also, if opt->priv->call_depth, create a