completion: teach archive to use __gitcomp_builtin

Currently, _git_archive() uses a hardcoded list of options for its
completion. However, we can use __gitcomp_builtin() to get a dynamically
generated list of completions instead.

Teach _git_archive() to use __gitcomp_builtin() so that newly
implemented options in archive will be automatically completed without
any mucking around in git-completion.bash. While we're at it, teach it
to complete the missing `--worktree-attributes` option as well.

Unfortunately, since some args are passed through from cmd_archive() to
write_archive() (which calls parse_archive_args()), there's no way that a
`--git-completion-helper` arg can end up reaching parse_archive_args()
since the first call to parse_options() will end up calling exit(0). As
a result, we have to carry the options supported by write_archive() in
the hardcoded string.

Signed-off-by: Denton Liu <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Denton-L

contrib/completion/git-completion.bash

@@ -1250,10 +1250,7 @@ _git_archive ()
 		return
 		;;
 	--*)
-		__gitcomp "
-			--format= --list --verbose
-			--prefix= --remote= --exec= --output
-			"
+		__gitcomp_builtin archive "--format= --list --verbose --prefix= --worktree-attributes"
 		return
 		;;
 	esac