Merge branch 'js/log-remerge-keep-ancestry'

"git log -p --remerge-diff --reverse" was completely broken.

* js/log-remerge-keep-ancestry:
  log: --remerge-diff needs to keep around commit parents

Author: gitster

builtin/log.c

@@ -528,10 +528,14 @@ static int cmd_log_walk_no_free(struct rev_info *rev)
 			 * but we didn't actually show the commit.
 			 */
 			rev->max_count++;
-		if (!rev->reflog_info) {
+		if (!rev->reflog_info && !rev->remerge_diff) {
 			/*
 			 * We may show a given commit multiple times when
-			 * walking the reflogs.
+			 * walking the reflogs. Therefore we still need it.
+			 *
+			 * Likewise, we potentially still need the parents
+			 * of * already shown commits to determine merge
+			 * bases when showing remerge diffs.
 			 */
 			free_commit_buffer(the_repository->parsed_objects,
 					   commit);

t/t4069-remerge-diff.sh

@@ -352,4 +352,11 @@ test_expect_success 'remerge-diff turns off history simplification' '
 	test_cmp expect actual
 '
 
+test_expect_success 'remerge-diff with --reverse' '
+	git log -1 --remerge-diff --oneline ab_resolution^ >expect &&
+	git log -1 --remerge-diff --oneline ab_resolution >>expect &&
+	git log -2 --remerge-diff --oneline ab_resolution --reverse >actual &&
+	test_cmp expect actual
+'
+
 test_done