Our git version is v2+ for some time now, but go.mod
still declared v1. Hopefully making both match makes
https://pkg.go.dev/github.com/rfjakob/gocryptfs/v2 work.
All the import paths have been fixed like this:
find . -name \*.go | xargs sed -i s%github.com/rfjakob/gocryptfs/%github.com/rfjakob/gocryptfs/v2/%
In response to the discussion of the xfstests mailing list [1],
I looked at the Lseek implementation, which was naive and
did not handle all cases correctly.
The new implementation aligns the returned values to 4096 bytes
as most callers expect.
A lot of tests are added to verify that we handle all
cases correctly now.
[1]: https://www.spinics.net/lists/fstests/msg16554.html
