.arcconfig

tests: write commit message using file I/O

Python 2.7 will print() \x94\x5c\x0a whereas Python 3 will
print() \xc2\x94\x5c\x0a. Why, I'm not sure. It probably has to
do with print() being Unicode aware on Python 3 and Python
attempting some kind of encoding before emitting the output.

This difference results in a different bytes making it to the
commit message and the JSON output varying. We work around
this by writing bytes to a commit message file.

Differential Revision: https://phab.mercurial-scm.org/D5741

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}