tests/readlink.py

perf: use the `perf--` prefix for perf command

This is the one command namespace where they should not be any ambiguity about
command that should be in it. The perf extensions is only adding performance
related command.

so this is a good ground to start putting dash folding to the tests.

Differential Revision: https://phab.mercurial-scm.org/D9516

#!/usr/bin/env python3

from __future__ import absolute_import, print_function

import errno
import os
import sys

for f in sys.argv[1:]:
    try:
        print(f, '->', os.readlink(f))
    except OSError as err:
        if err.errno != errno.EINVAL:
            raise
        print(f, '->', f, 'not a symlink')

sys.exit(0)