contrib/dumprevlog

rust: less set lookups in MissingAncestors

using the return values of HashSet::remove(), we can factor
pairs of `contains()/remove()` into a single `remove()`.

On a perfdiscovery run done on the PyPy repository, prepared
with contrib/discovery-helper.sh 50 100, I do get a modest improvement
with this (mean of medians of three runs is better by 2%)

Sample readings, before this change:

! wall 0.175609 comb 0.180000 user 0.180000 sys 0.000000 (median of 58)

With this change:

! wall 0.171662 comb 0.180000 user 0.170000 sys 0.010000 (median of 60)

Differential Revision: https://phab.mercurial-scm.org/D5943

#!/usr/bin/env python
# Dump revlogs as raw data stream
# $ find .hg/store/ -name "*.i" | xargs dumprevlog > repo.dump

from __future__ import absolute_import, print_function

import sys
from mercurial import (
    encoding,
    node,
    pycompat,
    revlog,
)
from mercurial.utils import (
    procutil,
)

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

def binopen(path, mode=b'rb'):
    if b'b' not in mode:
        mode = mode + b'b'
    return open(path, pycompat.sysstr(mode))

def printb(data, end=b'\n'):
    sys.stdout.flush()
    pycompat.stdout.write(data + end)

for f in sys.argv[1:]:
    r = revlog.revlog(binopen, encoding.strtolocal(f))
    print("file:", f)
    for i in r:
        n = r.node(i)
        p = r.parents(n)
        d = r.revision(n)
        printb(b"node: %s" % node.hex(n))
        printb(b"linkrev: %d" % r.linkrev(i))
        printb(b"parents: %s %s" % (node.hex(p[0]), node.hex(p[1])))
        printb(b"length: %d" % len(d))
        printb(b"-start-")
        printb(d)
        printb(b"-end-")