Summary:
In cases where cmount is not available in macOS, we alias nfsmount to mount command and transparently start the NFS server and mount it to the target dir.
The NFS server is started on localhost on a random port so it is reasonably secure.
Test Plan:
```
go run rclone.go mount --http-url https://beta.rclone.org :http: nfs-test
```
Added mount tests:
```
go test ./cmd/nfsmount
```
Since version 3 of fuse libfuse no longer does anything when given the
nonempty option and it's default is to allow mounting over non empty
directories like normal mount does.
Some versions of libfuse give an error when using `--allow-non-empty`
which is annoying for the user.
We now do this check ourselves so we no longer need to pass the option
to libfuse.
Fixes#3562
Before this change, the device name was always the remote:path rclone
was configured with. However this can contain sensitive information
and it appears in the `mount` output, so `--devname` allows the user
to configure it.
See: https://forum.rclone.org/t/rclone-mount-blomp-problem/29151/11
This is possible now that we no longer support go1.12 and brings
rclone into line with standard practices in the Go world.
This also removes errors.New and errors.Errorf from lib/errors and
prefers the stdlib errors package over lib/errors.
It was discovered `rclone mount` (but not `rclone cmount`) cached
directories after rename which it shouldn't have done.
This caused IO errors when trying to access files in renamed
directories on bucket based file systems.
This turned out to be the kernel caching the directories as basil/fuse
sets their expiry time to 60s for some reason.
This fix invalidates the relevant kernel cache entries in the for the
directories which fixes the problem.
Fixes: #4977
See: https://forum.rclone.org/t/after-a-directory-renmane-using-mv-files-are-not-visible-any-longer/22797
It turns out that NFS calls mknod in FUSE even though we have create
defined. This was causing EIO errors when creating files.
This patch fixes it by implementing mknod. The way it is implemented
means that to write to an NFS file system you'll need --vfs-cache-mode
writes.
This limit was previously 4k set in 59026c4761 however leaf
names above 1k now produce an IO error.
WinFSP seems to have its own method for dropping too long file names
above 255 long.
Before this change, the current working directory could disappear
according to the Linux kernel.
This was caused by mount returning different nodes with the same
information in.
This change uses vfs.Node.SetSys to cache the information so we always
return the same node.
The tests are now run for the mount commands and for the plain VFS.
This makes the tests much easier to debug when running with a VFS than
through a mount.
This problem was introduced in "mount: allow files of unkown size to
be read properly" 0baafb158f by failure to check that the
DirEntry was nil or not.
Before this change, files of unknown size (eg Google Docs) would
appear in file listings with 0 size and would only allow 0 bytes to be
read.
This change sets the direct_io flag in the FUSE return which bypasses
the cache for these files. This means that they can be read properly.
This is compatible with some, but not all applications.
Before this change rclone marked files opened for write without VFS
cache with the non seekable flag.
This caused problems with rclone mount layerd with mergerfs.
This change removes the hint and lets rclone do all the checking for
seekability.
