static char const * const builtin_commit_graph_usage[] = {
        N_("git commit-graph [--object-dir <objdir>]"),
        N_("git commit-graph read [--object-dir <objdir>]"),
-       N_("git commit-graph write [--object-dir <objdir>] [--stdin-packs|--stdin-commits]"),
+       N_("git commit-graph write [--object-dir <objdir>] [--append] [--stdin-packs|--stdin-commits]"),
        NULL
 };
 
 };
 
 static const char * const builtin_commit_graph_write_usage[] = {
-       N_("git commit-graph write [--object-dir <objdir>] [--stdin-packs|--stdin-commits]"),
+       N_("git commit-graph write [--object-dir <objdir>] [--append] [--stdin-packs|--stdin-commits]"),
        NULL
 };
 
        const char *obj_dir;
        int stdin_packs;
        int stdin_commits;
+       int append;
 } opts;
 
 static int graph_read(int argc, const char **argv)
                        N_("scan pack-indexes listed by stdin for commits")),
                OPT_BOOL(0, "stdin-commits", &opts.stdin_commits,
                        N_("start walk at commits listed by stdin")),
+               OPT_BOOL(0, "append", &opts.append,
+                       N_("include all commits already in the commit-graph file")),
                OPT_END(),
        };
 
                           pack_indexes,
                           packs_nr,
                           commit_hex,
-                          commits_nr);
+                          commits_nr,
+                          opts.append);
 
        return 0;
 }