phases: update the phase set as we go during retract boundary Apparently iterating over the `changed_revs` dictionary is very expensive. On mozilla-try-2019-02-18, a perf::unbundle call with a 10 000 changesets bundle gives give use the following timing. e57d4b868a3e: 4.6 seconds ac1c75188440: 102.5 seconds prev-changeset: 30.0 seconds this-changeset: 4.6 seconds So, the performance regression is gone. Once again: thanks to marvelous Python!

#!/usr/bin/env python3
#
# This is literally `cat` but in python, one char at a time.
#
# see sigpipe-remote.py for details.

import io
import os
import sys


if isinstance(sys.stdout.buffer, io.BufferedWriter):
    print('SIGPIPE-WORKER: script need unbuffered output', file=sys.stderr)
    sys.exit(255)

while True:
    c = os.read(sys.stdin.fileno(), 1)
    os.write(sys.stdout.fileno(), c)