bundle: split out a helper function to compute and write prerequisites

The new helper compute_and_write_prerequistes() is ugly, but it
cannot be avoided.  Ideally we should avoid a function that computes
and does I/O at the same time, but the prerequisites lines in the
output needs the human readable title only to help the recipient of
the bundle.  The code copies them straight from the rev-list output
and immediately discards as no other internal computation needs that
information.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

bundle.c

@@ -270,33 +270,15 @@ static int write_pack_data(int bundle_fd, struct lock_file *lock, struct rev_inf
 	return 0;
 }
 
-int create_bundle(struct bundle_header *header, const char *path,
+static int compute_and_write_prerequisites(int bundle_fd,
+					   struct rev_info *revs,
 					   int argc, const char **argv)
 {
-	static struct lock_file lock;
-	int bundle_fd = -1;
-	int bundle_to_stdout;
-	int i, ref_count = 0;
-	struct strbuf buf = STRBUF_INIT;
-	struct rev_info revs;
 	struct child_process rls = CHILD_PROCESS_INIT;
+	struct strbuf buf = STRBUF_INIT;
 	FILE *rls_fout;
+	int i;
 
-	bundle_to_stdout = !strcmp(path, "-");
-	if (bundle_to_stdout)
-		bundle_fd = 1;
-	else
-		bundle_fd = hold_lock_file_for_update(&lock, path,
-						      LOCK_DIE_ON_ERROR);
-
-	/* write signature */
-	write_or_die(bundle_fd, bundle_signature, strlen(bundle_signature));
-
-	/* init revs to list objects for pack-objects later */
-	save_commit_buffer = 0;
-	init_revisions(&revs, NULL);
-
-	/* write prerequisites */
 	argv_array_pushl(&rls.args,
 			 "rev-list", "--boundary", "--pretty=oneline",
 			 NULL);
@@ -314,7 +296,7 @@ int create_bundle(struct bundle_header *header, const char *path,
 			if (!get_sha1_hex(buf.buf + 1, sha1)) {
 				struct object *object = parse_object_or_die(sha1, buf.buf);
 				object->flags |= UNINTERESTING;
-				add_pending_object(&revs, object, buf.buf);
+				add_pending_object(revs, object, buf.buf);
 			}
 		} else if (!get_sha1_hex(buf.buf, sha1)) {
 			struct object *object = parse_object_or_die(sha1, buf.buf);
@@ -325,6 +307,35 @@ int create_bundle(struct bundle_header *header, const char *path,
 	fclose(rls_fout);
 	if (finish_command(&rls))
 		return error(_("rev-list died"));
+	return 0;
+}
+
+int create_bundle(struct bundle_header *header, const char *path,
+		  int argc, const char **argv)
+{
+	static struct lock_file lock;
+	int bundle_fd = -1;
+	int bundle_to_stdout;
+	int i, ref_count = 0;
+	struct rev_info revs;
+
+	bundle_to_stdout = !strcmp(path, "-");
+	if (bundle_to_stdout)
+		bundle_fd = 1;
+	else
+		bundle_fd = hold_lock_file_for_update(&lock, path,
+						      LOCK_DIE_ON_ERROR);
+
+	/* write signature */
+	write_or_die(bundle_fd, bundle_signature, strlen(bundle_signature));
+
+	/* init revs to list objects for pack-objects later */
+	save_commit_buffer = 0;
+	init_revisions(&revs, NULL);
+
+	/* write prerequisites */
+	if (compute_and_write_prerequisites(bundle_fd, &revs, argc, argv))
+		return -1;
 
 	/* write references */
 	argc = setup_revisions(argc, argv, &revs, NULL);