addremove: comparing two empty files caused ZeroDivisionError
(found by Giorgos Keramidas)
adding he
llo
abort: '\n' and '\r' disallowed in filenames
adding he
llo
abort: '\n' and '\r' disallowed in filenames
adding hell
o
abort: '\n' and '\r' disallowed in filenames
adding hell
o
abort: '\n' and '\r' disallowed in filenames
f he
llo he
llo
f hell
o hell
o