rebase: update the rebase wrapping to works with hg 4.6
Mercurial core commit bd0086bd3af4 removed _makeextrafn hence breaking our
wrapping. Update the code to wrap rebaseruntime directly in a way that's
compatible with hg 4.1+.
#!/bin/sh
. $TESTDIR/testlib/pythonpath.sh
# This file holds logic that is used in many tests.
# It can be called in a test like this:
# $ . "$TESTDIR/testlib/topic_setup.sh"
# Enable obsolete markers and enable extensions
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers,exchange
[extensions]
rebase=
topic=
EOF