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
```
billy defines a common file system interface that is used in multiple go packages.
vfs.Handle implements billy.File mostly, only two methods needed to be added to
make it compliant.
An interface check is added as well.
This is a preliminary work for adding serve nfs command.
Before this change we ran the tests and the mount in the same process.
This could cause deadlocks and often did, and made the mount tests
very unreliable.
This fixes the problem by running the mount in a seperate process and
commanding it via a pipe over stdin/stdout.
In this commit
f4c40bf79d mount: add --devname to set the device name sent to FUSE for mount display
The --devname parameter was added. However it was soon noticed that
attempting to mount via the rc gave this error:
mount helper error: fusermount: unknown option 'fsname'
mount FAILED: fusermount: exit status 1
This was because the DeviceName (and VolumeName) parameter was never
being initialised when the mount was called via the rc.
The fix for this was to refactor the rc interface so it called the
same Mount method as the command line mount which initialised the
DeviceName and VolumeName parameters properly.
This also fixes the cmd/mount tests which were breaking in the same
way but since they aren't normally run on the CI we didn't notice.
Fixes#6044
Add --network-mode option to activate mounting as network drive without having to set volume prefix.
Add support for automatic drive letter assignment (not specific to network drive mounting).
Allow full network share unc path in --volname, which will also implicitely activate network drive mounting.
Allow full network share unc path as mountpoint, which will also implicitely activate network drive mounting, and the specified path will be used as volume prefix and the remote will be mounted on an automatically assigned drive letter instead.
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.
