nametransform: add Dir() function

Dir is like filepath.Dir but returns "" instead of ".".
This was already implemented in fusefrontend_reverse as saneDir().

We will need it in nametransform for the improved diriv caching.

1 files changed, 9 insertions, 0 deletions

diff --git a/internal/nametransform/diriv.go b/internal/nametransform/diriv.go
index 6746f04..87e7887 100644
--- a/internal/nametransform/diriv.go
+++ b/internal/nametransform/diriv.go
@@ -162,3 +162,12 @@ func (be *NameTransform) EncryptPathDirIV(plainPath string, rootDir string) (cip
 	be.DirIVCache.Store(parentDir, iv, cParentDir)
 	return cipherPath, nil
 }
+
+// Dir is like filepath.Dir but returns "" instead of ".".
+func Dir(path string) string {
+	d := filepath.Dir(path)
+	if d == "." {
+		return ""
+	}
+	return d
+}