transaction recovery issue?

[ThomasWaldmann]

See there: borgbackup/borg#2099

Not sure if the bug also happens with attic, but the suspicious code is also in attic:

https://github.com/jborg/attic/blob/0.16/attic/repository.py#L467

@jborg can you remember why you used "ab" (and not "wb") there?

At first glance, it seems to make no sense to append to an existing file, esp. if the file is a valid segment file that has already a MAGIC at the beginning and some entries in it, this would just add another MAGIC in the middle of the file (but that should not be there).

So, was that just a typo or is there some reason behind it?

[ThomasWaldmann]

header_fmt.unpack(b'ATTICSEGx')
(1230263361, 1195725635, 120) # crc, size, tag

So the size value to look for in exceptions is 1195725635.