contrib/debugcmdserver.py

match: use '' instead of '.' for root directory (API)

I think '' is generally a better value for the root directory than '.'
is. For example, os.path.join('', 'foo') => 'foo', while
os.path.join('.', 'foo') => './foo'.

This patch mostly makes it so we use '' internally in
match.py. However, it also affects the API in visitdir(),
visitchildrenset() and files(). The two former now also accept '' as
input. I've updated the callers of these methods. I've also added a
deprecation warning for passing '.' (for external callers). The only
caller I could find that was affected by files() returning '' instead
of '.' was in dirstate.walk(). I've updated that.

The next few patches show some workarounds we can remove by using ''
instead of '.'.

Differential Revision: https://phab.mercurial-scm.org/D6401

#!/usr/bin/env python
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

from __future__ import absolute_import, print_function
import struct
import sys

if len(sys.argv) != 2:
    print('usage: debugcmdserver.py FILE')
    sys.exit(1)

outputfmt = '>cI'
outputfmtsize = struct.calcsize(outputfmt)

if sys.argv[1] == '-':
    log = sys.stderr
else:
    log = open(sys.argv[1], 'a')

def read(size):
    data = sys.stdin.read(size)
    if not data:
        raise EOFError
    sys.stdout.write(data)
    sys.stdout.flush()
    return data

try:
    while True:
        header = read(outputfmtsize)
        channel, length = struct.unpack(outputfmt, header)
        log.write('%s, %-4d' % (channel, length))
        if channel in 'IL':
            log.write(' -> waiting for input\n')
        else:
            data = read(length)
            log.write(' -> %r\n' % data)
        log.flush()
except EOFError:
    pass
finally:
    if log != sys.stderr:
        log.close()