Mark parent directory as viewed when all files are viewed (#33958)

Fix #25644 

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/treelist_test.go

@@ -0,0 +1,60 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repo
+
+import (
+	"testing"
+
+	pull_model "code.gitea.io/gitea/models/pull"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/services/gitdiff"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTransformDiffTreeForWeb(t *testing.T) {
+	ret := transformDiffTreeForWeb(&gitdiff.DiffTree{Files: []*gitdiff.DiffTreeRecord{
+		{
+			Status:   "changed",
+			HeadPath: "dir-a/dir-a-x/file-deep",
+			HeadMode: git.EntryModeBlob,
+		},
+		{
+			Status:   "added",
+			HeadPath: "file1",
+			HeadMode: git.EntryModeBlob,
+		},
+	}}, map[string]pull_model.ViewedState{
+		"dir-a/dir-a-x/file-deep": pull_model.Viewed,
+	})
+
+	assert.Equal(t, WebDiffFileTree{
+		TreeRoot: WebDiffFileItem{
+			Children: []*WebDiffFileItem{
+				{
+					EntryMode:   "tree",
+					DisplayName: "dir-a/dir-a-x",
+					FullName:    "dir-a/dir-a-x",
+					Children: []*WebDiffFileItem{
+						{
+							EntryMode:   "",
+							DisplayName: "file-deep",
+							FullName:    "dir-a/dir-a-x/file-deep",
+							NameHash:    "4acf7eef1c943a09e9f754e93ff190db8583236b",
+							DiffStatus:  "changed",
+							IsViewed:    true,
+						},
+					},
+				},
+				{
+					EntryMode:   "",
+					DisplayName: "file1",
+					FullName:    "file1",
+					NameHash:    "60b27f004e454aca81b0480209cce5081ec52390",
+					DiffStatus:  "added",
+				},
+			},
+		},
+	}, ret)
+}