add merge command. means same thing as "update -m".
repo.addchangegroup method now returns number of heads modified and added,
so command line can tell whether update or merge needed. this makes
tiny change to ssh wire protocol, but change is backwards compatible.
pull command now returns 0 if no changes to pull.
#!/bin/sh
mkdir a
cd a
hg init
echo foo > t1
hg add t1
hg commit -m "1" -d "1000000 0"
cd ..
hg clone a b
cd a
echo foo > t2
hg add t2
hg commit -m "2" -d "1000000 0"
cd ../b
echo foo > t3
hg add t3
hg commit -m "3" -d "1000000 0"
hg push ../a
hg pull ../a
hg push ../a
hg up -m
hg commit -m "4" -d "1000000 0"
hg push ../a