security: harden WebDAV overwrite and multi-root routing

chfs-ng/internal/storage/multipath_test.go

@@ -0,0 +1,26 @@
+package storage
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestNewMultiKeepsDuplicateBasenames(t *testing.T) {
+	root := t.TempDir()
+	first := filepath.Join(root, "same")
+	second := filepath.Join(root, "other", "same")
+	if err := os.MkdirAll(first, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(second, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	m := NewMulti([]string{first, second})
+	if len(m.Roots) != 2 || len(m.Names) != 2 {
+		t.Fatalf("duplicate basename dropped: roots=%d names=%v", len(m.Roots), m.Names)
+	}
+	if m.Names[0] != "same" || m.Names[1] != "same-2" {
+		t.Fatalf("unexpected virtual names: %v", m.Names)
+	}
+}