Fix minor memory leak found by LeakSanitizer.

The callers of merge_recursive() and merge_ort_recursive() expects the
commit list passed in as the merge_bases parameter to be fully
consumed by the function and does not free it when the function
returns.  In normal cases, the commit list does get consumed, but when
the function returns early upon encountering an error, it forgets to
clean it up.

Fix this by freeing the list in the code paths for error returns.

Signed-off-by: Kevin Backhouse <kevinbackhouse@github.com>

merge-ort-wrappers.c

@@ -54,8 +54,10 @@ int merge_ort_recursive(struct merge_options *opt,
 	struct tree *head = repo_get_commit_tree(opt->repo, side1);
 	struct merge_result tmp;
 
-	if (unclean(opt, head))
+	if (unclean(opt, head)) {
+		free_commit_list(merge_bases);
 		return -1;
+	}
 
 	memset(&tmp, 0, sizeof(tmp));
 	merge_incore_recursive(opt, merge_bases, side1, side2, &tmp);

merge-ort.c

@@ -5070,8 +5070,10 @@ static void merge_ort_internal(struct merge_options *opt,
 		opt->branch1 = "Temporary merge branch 1";
 		opt->branch2 = "Temporary merge branch 2";
 		merge_ort_internal(opt, NULL, prev, next, result);
-		if (result->clean < 0)
+		if (result->clean < 0) {
+			free_commit_list(merge_bases);
 			return;
+		}
 		opt->branch1 = saved_b1;
 		opt->branch2 = saved_b2;
 		opt->priv->call_depth--;

merge-recursive.c

@@ -3652,14 +3652,18 @@ static int merge_recursive_internal(struct merge_options *opt,
 		opt->branch1 = "Temporary merge branch 1";
 		opt->branch2 = "Temporary merge branch 2";
 		if (merge_recursive_internal(opt, merged_merge_bases, iter->item,
-					     NULL, &merged_merge_bases) < 0)
-			return -1;
+					     NULL, &merged_merge_bases) < 0) {
+			clean = -1;
+			goto out;
+		}
 		opt->branch1 = saved_b1;
 		opt->branch2 = saved_b2;
 		opt->priv->call_depth--;
 
-		if (!merged_merge_bases)
-			return err(opt, _("merge returned no commit"));
+		if (!merged_merge_bases) {
+			clean = err(opt, _("merge returned no commit"));
+			goto out;
+		}
 	}
 
 	/*
@@ -3682,8 +3686,11 @@ static int merge_recursive_internal(struct merge_options *opt,
 				     repo_get_commit_tree(opt->repo,
 							  merged_merge_bases),
 				     &result_tree);
+
+out:
 	strbuf_release(&merge_base_abbrev);
 	opt->ancestor = NULL;  /* avoid accidental re-use of opt->ancestor */
+	free_commit_list(merge_bases);
 	if (clean < 0) {
 		flush_output(opt);
 		return clean;
@@ -3729,6 +3736,9 @@ static int merge_start(struct merge_options *opt, struct tree *head)
 	assert(!opt->record_conflict_msgs_as_headers);
 	assert(!opt->msg_header_prefix);
 
+	CALLOC_ARRAY(opt->priv, 1);
+	string_list_init_dup(&opt->priv->df_conflict_file_set);
+
 	/* Sanity check on repo state; index must match head */
 	if (repo_index_has_changes(opt->repo, head, &sb)) {
 		err(opt, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
@@ -3737,16 +3747,13 @@ static int merge_start(struct merge_options *opt, struct tree *head)
 		return -1;
 	}
 
-	CALLOC_ARRAY(opt->priv, 1);
-	string_list_init_dup(&opt->priv->df_conflict_file_set);
 	return 0;
 }
 
 static void merge_finalize(struct merge_options *opt)
 {
 	flush_output(opt);
-	if (!opt->priv->call_depth && opt->buffer_output < 2)
-		strbuf_release(&opt->obuf);
+	strbuf_release(&opt->obuf);
 	if (show(opt, 2))
 		diff_warn_rename_limit("merge.renamelimit",
 				       opt->priv->needed_rename_limit, 0);
@@ -3763,8 +3770,10 @@ int merge_trees(struct merge_options *opt,
 
 	assert(opt->ancestor != NULL);
 
-	if (merge_start(opt, head))
+	if (merge_start(opt, head)) {
+		merge_finalize(opt);
 		return -1;
+	}
 	clean = merge_trees_internal(opt, head, merge, merge_base, &ignored);
 	merge_finalize(opt);
 
@@ -3785,8 +3794,11 @@ int merge_recursive(struct merge_options *opt,
 	prepare_repo_settings(opt->repo);
 	opt->repo->settings.command_requires_full_index = 1;
 
-	if (merge_start(opt, repo_get_commit_tree(opt->repo, h1)))
+	if (merge_start(opt, repo_get_commit_tree(opt->repo, h1))) {
+		free_commit_list(merge_bases);
+		merge_finalize(opt);
 		return -1;
+	}
 	clean = merge_recursive_internal(opt, h1, h2, merge_bases, result);
 	merge_finalize(opt);