add support for streaming clone.
existing clone code uses pull to get changes from remote repo. is very
slow, uses lots of memory and cpu.
new clone code has server write file data straight to client, client
writes file data straight to disk. memory and cpu used are very low,
clone is much faster over lan.
new client can still clone with pull, can still clone from older servers.
new server can still serve older clients.
#!/bin/sh
mkdir t
cd t
hg init
echo import > port
hg add port
hg commit -m 0 -u spam -d '0 0'
echo export >> port
hg commit -m 1 -u eggs -d '1 0'
echo export > port
echo vaportight >> port
echo 'import/export' >> port
hg commit -m 2 -u spam -d '2 0'
echo 'import/export' >> port
hg commit -m 3 -u eggs -d '3 0'
head -n 3 port > port1
mv port1 port
hg commit -m 4 -u spam -d '4 0'
hg grep port port
echo 'FIXME: history is wrong here'
hg grep --all -nu port port
hg grep import port