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
#
mkdir t
cd t
hg init
echo 0 > a
echo 0 > b
echo 0 > t.h
mkdir t
echo 0 > t/x
hg ci -A -m m -d "1000000 0"
touch nottracked
hg locate a
hg locate NONEXISTENT
hg locate
hg rm a
hg ci -m m -d "1000000 0"
hg locate a
hg locate NONEXISTENT
hg locate
hg locate -r 0 a
hg locate -r 0 NONEXISTENT
hg locate -r 0
echo % -I/-X with relative path should work
cd t
hg locate
hg locate -I ../t
# test issue294
cd ..
rm -r t
hg locate t