tests/test-pull-pull-corruption

new extension: fetch -> combine pull and merge/update

pull changes from remote repo.
if changes add new head: merge with new head, commit result.
else: update working dir to new head.

this makes useful command like git 'pull' command.

#!/bin/sh
#
# Corrupt an hg repo with two pulls.
#

# create one repo with a long history
hg init source1
cd source1
touch foo
hg add foo
for i in 1 2 3 4 5 6 7 8 9 10; do
    echo $i >> foo
    hg ci -m $i
done
cd ..

# create one repo with a shorter history
hg clone -r 0 source1 source2
cd source2
echo a >> foo
hg ci -m a
cd ..

# create a third repo to pull both other repos into it
hg init corrupted
cd corrupted
# use a hook to make the second pull start while the first one is still running
echo '[hooks]' >> .hg/hgrc
echo 'prechangegroup = sleep 5' >> .hg/hgrc

# start a pull...
hg pull ../source1 &

# ... and start another pull before the first one has finished
sleep 1
hg pull ../source2 2>/dev/null

# see the result
wait
hg verify