transactions: fix hg recover with fncache backups
The transaction backupfiles logic was broken for 'hg recover'. The file format
is XXX\0XXX\0YYY\0YYY\0 but the parser did a couple things wrong. 1) It went one
step beyond the final \0 and tried to read past the end of the array. 2)
array[i:i+1] returns a single item, instead of two items as intended.
Added a test to catch it, which turns out to be the first actual 'hg recover'
test.
#!/bin/sh
# This scripts is used to setup temp directory in memory
# for running Mercurial tests in vritual machine managed
# by Vagrant (see Vagrantfile for details).
cd /hgshared
make local
cd tests
mkdir /tmp/ram
sudo mount -t tmpfs -o size=100M tmpfs /tmp/ram
export TMPDIR=/tmp/ram
./run-tests.py -l --time