Fix diff view style handling (#36324)

Fix #36323

services/contexttest/context_tests.go

@@ -162,8 +162,10 @@ func LoadUser(t *testing.T, ctx gocontext.Context, userID int64) {
 	switch ctx := ctx.(type) {
 	case *context.Context:
 		ctx.Doer = doer
+		ctx.IsSigned = true
 	case *context.APIContext:
 		ctx.Doer = doer
+		ctx.IsSigned = true
 	default:
 		assert.FailNow(t, "context is not *context.Context or *context.APIContext")
 	}

services/gitdiff/gitdiff.go

@@ -200,6 +200,11 @@ type DiffBlobExcerptData struct {
 	AfterCommitID  string
 }
 
+const (
+	DiffStyleSplit   = "split"
+	DiffStyleUnified = "unified"
+)
+
 func (d *DiffLine) RenderBlobExcerptButtons(fileNameHash string, data *DiffBlobExcerptData) template.HTML {
 	dataHiddenCommentIDs := strings.Join(base.Int64sToStrings(d.SectionInfo.HiddenCommentIDs), ",")
 	anchor := fmt.Sprintf("diff-%sK%d", fileNameHash, d.SectionInfo.RightIdx)