contrib/undumprevlog

contrib: add a write microbenchmark to perf.py

I'm adding some performance logging to ui.write - this benchmark lets us
confirm that the cost of that logging is acceptably low.

At this point, the microbenchmark on Linux over SSH shows:

! wall 3.213560 comb 0.410000 user 0.350000 sys 0.060000 (best of 4)

while on the Mac locally, it shows:

! wall 0.342325 comb 0.180000 user 0.110000 sys 0.070000 (best of 20)

#!/usr/bin/env python
# Undump a dump from dumprevlog
# $ hg init
# $ undumprevlog < repo.dump

from __future__ import absolute_import

import sys
from mercurial import (
    node,
    revlog,
    scmutil,
    transaction,
    util,
)

for fp in (sys.stdin, sys.stdout, sys.stderr):
    util.setbinary(fp)

opener = scmutil.opener('.', False)
tr = transaction.transaction(sys.stderr.write, opener, {'store': opener},
                             "undump.journal")
while True:
    l = sys.stdin.readline()
    if not l:
        break
    if l.startswith("file:"):
        f = l[6:-1]
        r = revlog.revlog(opener, f)
        print f
    elif l.startswith("node:"):
        n = node.bin(l[6:-1])
    elif l.startswith("linkrev:"):
        lr = int(l[9:-1])
    elif l.startswith("parents:"):
        p = l[9:-1].split()
        p1 = node.bin(p[0])
        p2 = node.bin(p[1])
    elif l.startswith("length:"):
        length = int(l[8:-1])
        sys.stdin.readline() # start marker
        d = sys.stdin.read(length)
        sys.stdin.readline() # end marker
        r.addrevision(d, tr, lr, p1, p2)

tr.close()