lib: Get rid of buggy filesystem wrapping (#8257)

lib/fs/casefs.go

@@ -123,21 +123,27 @@ func (r *caseFilesystemRegistry) cleaner() {
 
 var globalCaseFilesystemRegistry = caseFilesystemRegistry{fss: make(map[fskey]*caseFilesystem)}
 
-// caseFilesystem is a BasicFilesystem with additional checks to make a
-// potentially case insensitive underlying FS behave like it's case-sensitive.
-type caseFilesystem struct {
-	Filesystem
-	realCaser
-}
-
-// NewCaseFilesystem ensures that the given, potentially case-insensitive filesystem
+// OptionDetectCaseConflicts ensures that the potentially case-insensitive filesystem
 // behaves like a case-sensitive filesystem. Meaning that it takes into account
 // the real casing of a path and returns ErrCaseConflict if the given path differs
 // from the real path. It is safe to use with any filesystem, i.e. also a
 // case-sensitive one. However it will add some overhead and thus shouldn't be
 // used if the filesystem is known to already behave case-sensitively.
-func NewCaseFilesystem(fs Filesystem) Filesystem {
-	return wrapFilesystem(fs, globalCaseFilesystemRegistry.get)
+type OptionDetectCaseConflicts struct{}
+
+func (o *OptionDetectCaseConflicts) apply(fs Filesystem) Filesystem {
+	return globalCaseFilesystemRegistry.get(fs)
+}
+
+func (o *OptionDetectCaseConflicts) String() string {
+	return "detectCaseConflicts"
+}
+
+// caseFilesystem is a BasicFilesystem with additional checks to make a
+// potentially case insensitive underlying FS behave like it's case-sensitive.
+type caseFilesystem struct {
+	Filesystem
+	realCaser
 }
 
 func (f *caseFilesystem) Chmod(name string, mode FileMode) error {