tests/mockblackbox.py

debugcommands: introduce actions to perform deterministic reads

"readavailable" is useful as a debugging device to see what data is
available on a pipe. But the mechanism isn't deterministic because
what's available on a pipe is highly conditional on timing, system
load, OS behavior, etc. This makes it not suitable for tests.

We introduce "ereadline," "read," and "eread" for performing
deterministic I/O operations (at least on blocking file descriptors).

We stop short of converting existing consumers of "readavailable"
in tests because we're working out race conditions and deadlocks
on Windows. But the goal is to eventually move tests away from
"readavailable" to these new APIs.

Differential Revision: https://phab.mercurial-scm.org/D2720

from __future__ import absolute_import
from mercurial import (
    util,
)

# XXX: we should probably offer a devel option to do this in blackbox directly
def getuser():
    return b'bob'
def getpid():
    return 5000

# mock the date and user apis so the output is always the same
def uisetup(ui):
    util.getuser = getuser
    util.getpid = getpid