fix: Prevent creating directories with no parent

pkg/fs/filesystem.go

@@ -283,6 +283,21 @@ func (f *STFS) Mkdir(name string, perm os.FileMode) error {
 	f.ioLock.Lock()
 	defer f.ioLock.Unlock()
 
+	if _, err := inventory.Stat(
+		f.metadata,
+
+		filepath.Dir(name),
+		false,
+
+		f.onHeader,
+	); err != nil {
+		if err == sql.ErrNoRows {
+			return os.ErrNotExist
+		}
+
+		return err
+	}
+
 	if hdr, err := inventory.Stat(
 		f.metadata,
 

pkg/fs/filesystem_test.go

@@ -806,13 +806,13 @@ var mkdirTests = []struct {
 	wantErr bool
 }{
 	{
-		"Can create directory /test.txt",
-		mkdirArgs{"/test.txt", os.ModePerm},
+		"Can create directory /test",
+		mkdirArgs{"/test", os.ModePerm},
 		false,
 	},
 	{
-		"Can create directory /test.txt with different permissions",
-		mkdirArgs{"/test.txt", 0666},
+		"Can create directory /test with different permissions",
+		mkdirArgs{"/test", 0666},
 		false,
 	},
 	{
@@ -830,12 +830,11 @@ var mkdirTests = []struct {
 		mkdirArgs{"", os.ModePerm},
 		true,
 	},
-	// FIXME: STFS can create directory in non-existent directory, which should not be possible
-	// {
-	// 	"Can not create /nonexistent/test.txt",
-	// 	mkdirArgs{"/nonexistent/test.txt", os.ModePerm},
-	// 	true,
-	// },
+	{
+		"Can not create /nonexistent/test",
+		mkdirArgs{"/nonexistent/test", os.ModePerm},
+		true,
+	},
 }
 
 func TestSTFS_Mkdir(t *testing.T) {