tests/readlink.py

tests: use $HTTP_DATE$ for Date header

Support for the $HTTP_DATE$ substitution was recently added. Let's
adopt it more widely.

We had to tweak the substitution to be case insensitive, since
HTTP headers are case insensitive. I also found a minor test
issue not globbing over the length of the Server response header.

Differential Revision: https://phab.mercurial-scm.org/D2839

#!/usr/bin/env python

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)