Calculate filename hash only once (#19654)

* Calculate hash only once.

* remove unused Sha1 template helper function, use ctx.Data["FileNameHash"]

* fix unit tests

services/repository/files/diff_test.go

@@ -37,6 +37,7 @@ func TestGetDiffPreview(t *testing.T) {
 			{
 				Name:        "README.md",
 				OldName:     "README.md",
+				NameHash:    "8ec9a00bfd09b3190ac6b22251dbb1aa95a0579d",
 				Index:       1,
 				Addition:    2,
 				Deletion:    1,
@@ -123,7 +124,7 @@ func TestGetDiffPreview(t *testing.T) {
 		assert.NoError(t, err)
 		bs, err := json.Marshal(diff)
 		assert.NoError(t, err)
-		assert.EqualValues(t, expectedBs, bs)
+		assert.EqualValues(t, string(expectedBs), string(bs))
 	})
 
 	t.Run("empty branch, same results", func(t *testing.T) {