fuse: allow setting the fsname (first column in df -T)

fuse/api.go

@@ -53,8 +53,10 @@ type MountOptions struct {
 	// This may be useful for NFS.
 	RememberInodes bool
 
-	// The name will show up on the output of the mount. Keep this string
-	// small.
+	// Values shown in "df -T" and friends
+	// First column, "Filesystem"
+	FsName string
+	// Second column, "Type", will be shown as "fuse." + Name
 	Name string
 
 	// If set, wrap the file system in a single-threaded locking wrapper.

fuse/server.go

@@ -165,6 +165,11 @@ func NewServer(fs RawFileSystem, mountPoint string, opts *MountOptions) (*Server
 	}
 	optStrs = append(optStrs, "subtype="+name)
 
+	fsname := opts.FsName
+	if len(fsname) > 0 {
+		optStrs = append(optStrs, "fsname="+fsname)
+	}
+
 	mountPoint = filepath.Clean(mountPoint)
 	if !filepath.IsAbs(mountPoint) {
 		cwd, err := os.Getwd()