topics: add t0 and b0 to the stack
t0 or b0 will be the base of the stack and it's the parent of t1 or b1. The cool
thing about this is that if you update to t0 using `hg up t0` or do `hg prev` on
t1, you will be updated to t0 with the current topic preserved.
This patch adds t0 to stack and implement the preserving topic case for t0 while
using `hg update`.
# setup config and various utility to test new heads checks on push
. $TESTDIR/testlib/common.sh
cat >> $HGRCPATH <<EOF
[ui]
# simpler log output
logtemplate ="{node|short} ({phase}): {desc}\n"
[phases]
# non publishing server
publish=False
[extensions]
# we need to strip some changeset for some test cases
strip=
evolve=
EOF
setuprepos() {
echo creating basic server and client repo
hg init server
cd server
mkcommit root
hg phase --public .
mkcommit A0
cd ..
hg clone server client
}