localrepo/branchcache: kill unused localrepo.branchcache
The UTF-8 version of the branchcache is the master, always up-to-date, we can
rename it to localrepo._branchcache.
#!/bin/sh
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
ls
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "1000000 0"
hg co 0
# B should disappear
ls