[test] add unit tests for ruleset
We extract the rules building logic from readfile into a Ruleset.buildrules()
method to ease testing.
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