tests/narrow-library.sh

subrepo: access status members by name instead of by position

Taking my first Mercurial project closer to completion.

Differential Revision: https://phab.mercurial-scm.org/D5144

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