stack: extra argument validation logic outside of showstack
It seems sensible keep the 'showstack' function purely about actually displaying
and existing stack.
#!/bin/sh
# This file holds logic that is used in many tests.
# It can be called in a test like this:
# $ . "$TESTDIR/testlib"
# Enable obsolete markers and enable extensions
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers,exchange
[extensions]
rebase=
EOF
echo "topic=$(echo $(dirname $TESTDIR))/hgext3rd/topic" >> $HGRCPATH