commit-graph: collapse parameters into flags

The write_commit_graph() and write_commit_graph_reachable() methods
currently take two boolean parameters: 'append' and 'report_progress'.
As we update these methods, adding more parameters this way becomes
cluttered and hard to maintain.

Collapse these parameters into a 'flags' parameter, and adjust the
callers to provide flags as necessary.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 2a1c4d7..d8efa5b 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -142,6 +142,7 @@ static int graph_write(int argc, const char **argv)
 	struct string_list *commit_hex = NULL;
 	struct string_list lines;
 	int result = 0;
+	unsigned int flags = COMMIT_GRAPH_PROGRESS;
 
 	static struct option builtin_commit_graph_write_options[] = {
 		OPT_STRING(0, "object-dir", &opts.obj_dir,
@@ -166,11 +167,13 @@ static int graph_write(int argc, const char **argv)
 		die(_("use at most one of --reachable, --stdin-commits, or --stdin-packs"));
 	if (!opts.obj_dir)
 		opts.obj_dir = get_object_directory();
+	if (opts.append)
+		flags |= COMMIT_GRAPH_APPEND;
 
 	read_replace_refs = 0;
 
 	if (opts.reachable)
-		return write_commit_graph_reachable(opts.obj_dir, opts.append, 1);
+		return write_commit_graph_reachable(opts.obj_dir, flags);
 
 	string_list_init(&lines, 0);
 	if (opts.stdin_packs || opts.stdin_commits) {
@@ -190,8 +193,7 @@ static int graph_write(int argc, const char **argv)
 	if (write_commit_graph(opts.obj_dir,
 			       pack_indexes,
 			       commit_hex,
-			       opts.append,
-			       1))
+			       flags))
 		result = 1;
 
 	UNLEAK(lines);