hgext/fsmonitor/pywatchman/compat.py

wireprotov2: advertise recommended batch size for requests

Currently, exchangev2 hardcodes the batch size for how many revisions
to fetch per command request. A single value is not appropriate
for every repository because some repositories may have a drastically
different "shape" from other repositories. e.g. a repo with lots of
small files may benefit from larger batch sizes than a repo with lots
of large files. And depending on caching used by the server, the server
may wish to control the number of commands (to e.g. mitigate overhead
of following content redirects).

This commit teaches wireprotov2 commands to declare extra metadata
which is advertised as part of the command descriptor. The manifestdata
command has been taught to advertise a recommended batch size for
requests.

Differential Revision: https://phab.mercurial-scm.org/D4975

# Copyright 2016-present Facebook, Inc.
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from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
# no unicode literals

'''Compatibility module across Python 2 and 3.'''

import sys

PYTHON3 = sys.version_info >= (3, 0)

# This is adapted from https://bitbucket.org/gutworth/six, and used under the
# MIT license. See LICENSE for a full copyright notice.
if PYTHON3:
    def reraise(tp, value, tb=None):
        try:
            if value is None:
                value = tp()
            if value.__traceback__ is not tb:
                raise value.with_traceback(tb)
            raise value
        finally:
            value = None
            tb = None
else:
    exec('''
def reraise(tp, value, tb=None):
    try:
        raise tp, value, tb
    finally:
        tb = None
'''.strip())

if PYTHON3:
    UNICODE = str
else:
    UNICODE = unicode