bundle: split out a helper function to create pack data

The create_bundle() function, while it does one single logical
thing, takes a rather large implementation to do so.

Let's start separating what it does into smaller steps to make it
easier to see what is going on.  This is a first step to separate
out the actual pack-data generation, after the earlier part of the
function figures out which part of the history to place in the
bundle.

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

bundle.c

@@ -235,6 +235,41 @@ out:
 	return result;
 }
 
+static int write_pack_data(int bundle_fd, struct lock_file *lock, struct rev_info *revs)
+{
+	struct child_process pack_objects = CHILD_PROCESS_INIT;
+	int i;
+
+	argv_array_pushl(&pack_objects.args,
+			 "pack-objects", "--all-progress-implied",
+			 "--stdout", "--thin", "--delta-base-offset",
+			 NULL);
+	pack_objects.in = -1;
+	pack_objects.out = bundle_fd;
+	pack_objects.git_cmd = 1;
+	if (start_command(&pack_objects))
+		return error(_("Could not spawn pack-objects"));
+
+	/*
+	 * start_command closed bundle_fd if it was > 1
+	 * so set the lock fd to -1 so commit_lock_file()
+	 * won't fail trying to close it.
+	 */
+	lock->fd = -1;
+
+	for (i = 0; i < revs->pending.nr; i++) {
+		struct object *object = revs->pending.objects[i].item;
+		if (object->flags & UNINTERESTING)
+			write_or_die(pack_objects.in, "^", 1);
+		write_or_die(pack_objects.in, sha1_to_hex(object->sha1), 40);
+		write_or_die(pack_objects.in, "\n", 1);
+	}
+	close(pack_objects.in);
+	if (finish_command(&pack_objects))
+		return error(_("pack-objects died"));
+	return 0;
+}
+
 int create_bundle(struct bundle_header *header, const char *path,
 		  int argc, const char **argv)
 {
@@ -381,34 +416,9 @@ int create_bundle(struct bundle_header *header, const char *path,
 	write_or_die(bundle_fd, "\n", 1);
 
 	/* write pack */
-	child_process_init(&rls);
-	argv_array_pushl(&rls.args,
-			 "pack-objects", "--all-progress-implied",
-			 "--stdout", "--thin", "--delta-base-offset",
-			 NULL);
-	rls.in = -1;
-	rls.out = bundle_fd;
-	rls.git_cmd = 1;
-	if (start_command(&rls))
-		return error(_("Could not spawn pack-objects"));
+	if (write_pack_data(bundle_fd, &lock, &revs))
+		return -1;
 
-	/*
-	 * start_command closed bundle_fd if it was > 1
-	 * so set the lock fd to -1 so commit_lock_file()
-	 * won't fail trying to close it.
-	 */
-	lock.fd = -1;
-
-	for (i = 0; i < revs.pending.nr; i++) {
-		struct object *object = revs.pending.objects[i].item;
-		if (object->flags & UNINTERESTING)
-			write_or_die(rls.in, "^", 1);
-		write_or_die(rls.in, sha1_to_hex(object->sha1), 40);
-		write_or_die(rls.in, "\n", 1);
-	}
-	close(rls.in);
-	if (finish_command(&rls))
-		return error(_("pack-objects died"));
 	if (!bundle_to_stdout) {
 		if (commit_lock_file(&lock))
 			die_errno(_("cannot create '%s'"), path);