extend network protocol to stop clients from locking servers now all repositories have capabilities slot, tuple with list of names. if 'unbundle' capability present, repo supports push where client does not need to lock server. repository classes that have unbundle capability also have unbundle method. implemented for ssh now, will be base for push over http. unbundle protocol acts this way. server tells client what heads it has during normal negotiate step. client starts unbundle by repeat server's heads back to it. if server has new heads, abort immediately. otherwise, transfer changes to server. once data transferred, server locks and checks heads again. if heads same, changes can be added. else someone else added heads, and server aborts. if client wants to force server to add heads, sends special heads list of 'force'.

#!/bin/sh

cat <<'EOF' > merge
#!/bin/sh
echo merging for `basename $1`
EOF
chmod +x merge
HGMERGE=./merge; export HGMERGE

mkdir A1
cd A1
hg init
echo This is file foo1 > foo
echo This is file bar1 > bar
hg add foo bar
hg commit -m "commit text" -d "1000000 0"

cd ..
hg clone A1 B1

cd A1
rm bar
hg remove bar
hg commit -m "commit test" -d "1000000 0"

cd ../B1
echo This is file foo22 > foo
hg commit -m "commit test" -d "1000000 0"

cd ..
hg clone A1 A2
hg clone B1 B2

cd A1
hg pull ../B1
hg merge
hg commit -m "commit test" -d "1000000 0"
echo bar should remain deleted.
hg manifest

cd ../B2
hg pull ../A2
hg merge
hg commit -m "commit test" -d "1000000 0"
echo bar should remain deleted.
hg manifest