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.
#require test-repo pyflakes
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"
tests/filterpyflakes.py:58: undefined name 'undefinedname'