Revert "builtin-archive: use RUN_SETUP"

Commit 64edf4b2 cleaned up the initialization of git-archive,
at the cost of 'git-archive --list' now requiring a git repo.
This patch reverts the cleanup and documents the requirement
for this particular dirtyness in a test.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-archive.c

@@ -252,6 +252,8 @@ int cmd_archive(int argc, const char **argv, const char *prefix)
 
 	memset(&ar, 0, sizeof(ar));
 	tree_idx = parse_archive_args(argc, argv, &ar);
+	if (prefix == NULL)
+		prefix = setup_git_directory();
 
 	argv += tree_idx;
 	parse_treeish_arg(argv, &ar.args, prefix);