added test for file name normalization with leading dot

tools/filesystem/file_test.go

@@ -215,6 +215,7 @@ func TestFileNameNormalizations(t *testing.T) {
 		{"a.b.c.?.?.?.2", `^a_b_c_\w{10}\.2$`},
 		{"a.b.c.d.tar.gz", `^a_b_c_d_\w{10}\.tar\.gz$`},
 		{"abcd", `^abcd_\w{10}\.txt$`},
+		{".abcd.123.", `^abcd_\w{10}\.123$`},
 		{"a  b! c d  . 456", `^a_b_c_d_\w{10}\.456$`},                                        // normalize spaces
 		{strings.Repeat("a", 101) + "." + strings.Repeat("b", 21), `^a{100}_\w{10}\.b{20}$`}, // name and extension length trim
 	}
@@ -225,7 +226,8 @@ func TestFileNameNormalizations(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			if match, err := regexp.Match(s.pattern, []byte(f.Name)); !match {
+			match, err := regexp.Match(s.pattern, []byte(f.Name))
+			if !match {
 				t.Fatalf("Expected Name to match %v, got %q (%v)", s.pattern, f.Name, err)
 			}
 		})