Store empty (default) branch in branch cache, too.
Operations on this branch don't work otherwise.
Reading branches.cache had to be adjusted to allow an empty label.
Adjusted reading of the cache tip for symmetry, no functional change here.
#!/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 a third repo to pull both other repos into it
hg init version2
hg -R version2 pull source1 &
sleep 1
hg clone --pull -U version2 corrupted
wait
hg -R corrupted verify
hg -R version2 verify