tests: use graph log in {latesttag} tests
The tests are much easier to read if one does not have to re-read the
setup part all the time to understand the graph shape.
Differential Revision: https://phab.mercurial-scm.org/D446
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state