lib/fs: Expose fs option on interface (fixes #7385, ref #7381) (#7389)

lib/fs/filesystem.go

@@ -47,6 +47,7 @@ type Filesystem interface {
 	Usage(name string) (Usage, error)
 	Type() FilesystemType
 	URI() string
+	Options() []Option
 	SameFile(fi1, fi2 FileInfo) bool
 }
 
@@ -178,9 +179,15 @@ var IsPermission = os.IsPermission
 // IsPathSeparator is the equivalent of os.IsPathSeparator
 var IsPathSeparator = os.IsPathSeparator
 
-type Option struct {
-	apply func(Filesystem)
-	id    string
+// Option modifies a filesystem at creation. An option might be specific
+// to a filesystem-type.
+//
+// String is used to detect options with the same effect, i.e. must be different
+// for options with different effects. Meaning if an option has parameters, a
+// representation of those must be part of the returned string.
+type Option interface {
+	String() string
+	apply(Filesystem)
 }
 
 func NewFilesystem(fsType FilesystemType, uri string, opts ...Option) Filesystem {