largefiles: don't require a user cache (issue3088) (issue3155)
If the user cache path isn't specified in .hgrc, and it can't be constructed
from the environment, don't try to use that cache.
Test hangup signal in the middle of transaction
$ "$TESTDIR/hghave" fifo || exit 80
$ hg init
$ mkfifo p
$ hg serve --stdio < p &
$ P=$!
$ (echo lock; echo addchangegroup; sleep 5) > p &
$ Q=$!
$ sleep 3
0
0
adding changesets
$ kill -HUP $P
$ wait
transaction abort!
rollback completed
killed!
$ echo .hg/* .hg/store/*
.hg/00changelog.i .hg/journal.bookmarks .hg/journal.branch .hg/journal.desc .hg/journal.dirstate .hg/requires .hg/store .hg/store/00changelog.i .hg/store/00changelog.i.a