tests/readlink.py

shortest: make pure code also disambigute against revnums at end

This makes the pure code more similar to the native code in that it
first finds a prefix that's unambiguous among nodeids and then adds
hex digits until it no longer looks like a revnum. It will allow us to
even better separate the disambiguation with revnums in a later patch.

With this patch `hg log -r 0::50 -T '{shortest(node,1)}'` with no
native code goes from 25s to 43s. It wasn't exactly usable to begin
with, so I don't feel too bad about it.

Differential Revision: https://phab.mercurial-scm.org/D3500

#!/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)