stream-clone: disable gc for the initial section for the v3 format The number of small container created turn Python in a gc-frenzy that seriously impact performance. This significantly boost performance. The following number comes from a large private repository using perf::stream-locked-section: base-line: 35.04 seconds prev-change: 24.51 seconds (-30%) prev-change: 20.88 seconds (-40%) this-change: 14.22 seconds (-60% from baseline; -31% from prev)

# extension to emulate interrupting filemerge._filemerge


from mercurial import (
    error,
    extensions,
    filemerge,
)


def failfilemerge(*args, **kwargs):
    raise error.Abort(b"^C")


def extsetup(ui):
    extensions.wrapfunction(filemerge, 'filemerge', failfilemerge)