evolve: use right value for branch name when finding branch heads subbranch already formatted as "branchname:topicname", again appending it with ":topicname" doesn't not make sense. It's a little bit surprising that no tests fails though.

. $TESTDIR/testlib/common.sh

cat >> $HGRCPATH <<EOF
[ui]
interactive = true
[phases]
publish=False
[extensions]
evolve =
[experimental]
evolution.effect-flags = yes
EOF

sync() {
   hg pull -R $TESTTMP/server . -q
}