tests/narrow-library.sh

tests: extract printrevset extension from test-glog-beautifygraph.t

Differential Revision: https://phab.mercurial-scm.org/D4251

cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=python "$TESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF