tests/unwrap-message-id.py

help: explain in `hg help flags` that unambiguous prefixes are allowed

I used `hg commit --amend` as an example because that's the most
frequently used flag I could think of that doesn't yet have a short
form.

Differential Revision: https://phab.mercurial-scm.org/D8607

from __future__ import absolute_import, print_function

import sys

for line in sys.stdin:
    if line.lower() in ("message-id: \n", "in-reply-to: \n"):
        line = line[:-2]
    print(line, end="")