tests: extract obshistory setup in a separate file
We are gonna soon explode the obshistory test file into several, extract the
setup to reuse it as much as possible.
. $TESTDIR/testlib/common.sh
cat >> $HGRCPATH <<EOF
[ui]
interactive = true
[phases]
publish=False
[extensions]
evolve =
[experimental]
evolution.effect-flags = yes
EOF