tests/test-revlog-mmapindex.t

py3: allow run-tests.py to run on Windows

This is now functional:

    HGMODULEPOLICY=py py -3 run-tests.py --local test-help.t --pure --view bcompare

However, on this machine without a C compiler, it tries to load cext anyway, and
blows up.  I haven't looked into why, other than to see that it does set the
environment variable.  When the test exits though, I see it can't find
killdaemons.py, get-with-headers.py, etc.

I have no idea why these changes are needed, given that it runs on Linux.  But
os.system() is insisting that it take a str, and subprocess.Popen() blows up
without str:

    Errored test-help.t: Traceback (most recent call last):
      File "run-tests.py", line 810, in run
        self.runTest()
      File "run-tests.py", line 858, in runTest
        ret, out = self._run(env)
      File "run-tests.py", line 1268, in _run
        exitcode, output = self._runcommand(cmd, env)
      File "run-tests.py", line 1141, in _runcommand
        env=env)
      File "C:\Program Files\Python37\lib\subprocess.py", line 756, in __init__
        restore_signals, start_new_session)
      File "C:\Program Files\Python37\lib\subprocess.py", line 1100, in _execute_child
        args = list2cmdline(args)
      File "C:\Program Files\Python37\lib\subprocess.py", line 511, in list2cmdline
        needquote = (" " in arg) or ("\t" in arg) or not arg
    TypeError: argument of type 'int' is not iterable

This is exactly how it crashes when trying to spin up a pager too.  I left one
instance of os.system() unchanged in _installhg(), because it doesn't get there.

create verbosemmap.py
  $ cat << EOF > verbosemmap.py
  > # extension to make util.mmapread verbose
  > 
  > from __future__ import absolute_import
  > 
  > from mercurial import (
  >     extensions,
  >     pycompat,
  >     util,
  > )
  > 
  > def extsetup(ui):
  >     def mmapread(orig, fp):
  >         ui.write(b"mmapping %s\n" % pycompat.bytestr(fp.name))
  >         ui.flush()
  >         return orig(fp)
  > 
  >     extensions.wrapfunction(util, 'mmapread', mmapread)
  > EOF

setting up base repo
  $ hg init a
  $ cd a
  $ touch a
  $ hg add a
  $ hg commit -qm base
  $ for i in `$TESTDIR/seq.py 1 100` ; do
  > echo $i > a
  > hg commit -qm $i
  > done

set up verbosemmap extension
  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > verbosemmap=$TESTTMP/verbosemmap.py
  > EOF

mmap index which is now more than 4k long
  $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=4k
  mmapping $TESTTMP/a/.hg/store/00changelog.i
  100
  99
  98
  97
  96

do not mmap index which is still less than 32k
  $ hg log -l 5 -T '{rev}\n' --config experimental.mmapindexthreshold=32k
  100
  99
  98
  97
  96

  $ cd ..