+static int parse_parent_arg_callback(const struct option *opt,
+ const char *arg, int unset)
+{
+ struct object_id oid;
+ struct commit_list **parents = opt->value;
+
+ BUG_ON_OPT_NEG_NOARG(unset, arg);
+
+ if (get_oid_commit(arg, &oid))
+ die(_("not a valid object name %s"), arg);
+
+ assert_oid_type(&oid, OBJ_COMMIT);
+ new_parent(lookup_commit(the_repository, &oid), parents);
+ return 0;
+}
+
+static int parse_message_arg_callback(const struct option *opt,
+ const char *arg, int unset)
+{
+ struct strbuf *buf = opt->value;
+
+ BUG_ON_OPT_NEG_NOARG(unset, arg);
+
+ if (buf->len)
+ strbuf_addch(buf, '\n');
+ strbuf_addstr(buf, arg);
+ strbuf_complete_line(buf);
+
+ return 0;
+}
+
+static int parse_file_arg_callback(const struct option *opt,
+ const char *arg, int unset)
+{
+ int fd;
+ struct strbuf *buf = opt->value;
+
+ BUG_ON_OPT_NEG_NOARG(unset, arg);
+
+ if (buf->len)
+ strbuf_addch(buf, '\n');
+ if (!strcmp(arg, "-"))
+ fd = 0;
+ else {
+ fd = open(arg, O_RDONLY);
+ if (fd < 0)
+ die_errno(_("git commit-tree: failed to open '%s'"), arg);
+ }
+ if (strbuf_read(buf, fd, 0) < 0)
+ die_errno(_("git commit-tree: failed to read '%s'"), arg);
+ if (fd && close(fd))
+ die_errno(_("git commit-tree: failed to close '%s'"), arg);
+
+ return 0;
+}
+