Use repo vfs to join the server log
The method join on repo has been removed in changeset edb7f628ef8b of
mercurial.
if ${CHROOT_TEST_INSTALLDEB:-false} ; then
cp build/debian/*.deb $BACKING/action
else
hg st -mac0n -X '.hg*' -X 'dev/**' \
| cpio -p -0 -d $BACKING/action/mercurial-server
fi