Only the `Sys()` value from os.FileInfo is kept as field `sys` to
support Windows. The os.FileInfo removal ensures that for values like
`ModTime` that existed in both data structures there's no more confusion
which value is actually used.
Extended attributes and security descriptors apparently cannot be
retrieved from a vss volume. Fix the volume check to correctly detect
vss volumes and just completely disable extended attributes for volumes.
Previously, nodeRestoreTimestamps would do something like
if node.Type == restic.NodeTypeSymlink {
return nodeRestoreSymlinkTimestamps(...)
}
return syscall.UtimesNano(...)
where nodeRestoreSymlinkTimestamps was either a no-op or a
reimplementation of syscall.UtimesNano that handles symlinks, with some
repeated converting between timestamp types. The Linux implementation
was a bit clumsy, requiring three syscalls to set the timestamps.
In this new setup, there is a function utimesNano that has three
implementations:
* on Linux, it's a modified syscall.UtimesNano that uses
AT_SYMLINK_NOFOLLOW and AT_FDCWD so it can handle any type in a single
call;
* on other Unix platforms, it just calls the syscall function after
skipping symlinks;
* on Windows, it's the modified UtimesNano that was previously called
nodeRestoreSymlinkTimestamps, except with different arguments.
This does not produce exactly the same messages, as it inserts newlines
instead of "; ". But given how long our error messages can be, that
might be a good thing.
