The upstream library rclone uses for rclone mount no longer supports
freebsd. Not only is it broken, but it no longer compiles.
This patch disables rclone mount for freebsd.
However all is not lost for freebsd users - compiling rclone with the
`cmount` tag, so `go install -tags cmount` will install a working
`rclone mount` command which uses cgofuse and the libfuse C library
directly.
Note that the binaries from rclone.org will not have mount support as
we don't have a freebsd build machine in CI and it is very hard to
cross compile cmount.
See: https://github.com/bazil/fuse/issues/280Fixes#5843
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
```
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.
The written out list of tests was replaced with a nested test for
mount and cmount. The tests for each VFS cache mode were also replaced
with nested tests which makes the output and the code much cleaner.
