upgraderepo: add a config option for parallel computation
The option is put to use to compute new copy tracing side data in parallel. It
use the multiprocessing module as it had the appropriate primitive for what we
needed. Gregory Szorc had concerned on windows so we disabled it there.
See inline comment for details on the parallel implementation.
#require vcr
$ cat >> $HGRCPATH <<EOF
> [extensions]
> phabricator =
> EOF
$ hg init repo
$ cd repo
$ cat >> .hg/hgrc <<EOF
> [phabricator]
> url = https://phab.mercurial-scm.org/
> callsign = HG
>
> [auth]
> hgphab.schemes = https
> hgphab.prefix = phab.mercurial-scm.org
> # When working on the extension and making phabricator interaction
> # changes, edit this to be a real phabricator token. When done, edit
> # it back. The VCR transcripts will be auto-sanitised to replace your real
> # token with this value.
> hgphab.phabtoken = cli-hahayouwish
> EOF
$ VCR="$TESTDIR/phabricator"