heptapod-ci: add a script to map evolve branch to mercurial revision for tests
map-hg-rev.sh can be tested using this command:
```sh
for i in $(hg log -T '{branch}\n' | sort -u); do
echo $i $(testlib/map-hg-rev.sh $i)
done
```
#!/bin/sh
. $TESTDIR/testlib/pythonpath.sh
# This file holds logic that is used in many tests.
# It can be called in a test like this:
# $ . "$TESTDIR/testlib/topic_setup.sh"
# Enable obsolete markers and enable extensions
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers,exchange
[extensions]
rebase=
topic=
EOF