feat(diff): Add search and extension filter to diff sidebar (#37068)

Adds a search box and a file-extension filter to the pull request diff
sidebar, so reviewers can narrow a large diff down to the files they
care about.

Both filters apply to the file tree and to the diff itself. The
extension menu follows GitHub: extensions sorted alphabetically,
dotfiles and extension-less files in their own buckets, and the
selection kept in the same `file-filters[]` query parameter, so a
filtered view is shareable and survives a reload.

The menu can list every extension in a diff, so `createTippy` gains an
opt-in `limitSizeToViewport` option that caps a popup to the space left
in the viewport and scrolls its content. Popups that do not ask for it
are unchanged.

Closes https://github.com/go-gitea/gitea/issues/27256
Signed-off-by: silverwind <me@silverwind.io>
Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: Copilot <copilot@github.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/treelist.go

@@ -63,6 +63,7 @@ func isExcludedEntry(entry *git.TreeEntry) bool {
 // WebDiffFileItem is used by frontend, check the field names in frontend before changing
 type WebDiffFileItem struct {
 	FullName    string
+	OldFullName string
 	DisplayName string
 	NameHash    string
 	DiffStatus  string
@@ -110,6 +111,9 @@ func transformDiffTreeForWeb(renderedIconPool *fileicon.RenderedIconPool, diffTr
 
 	for _, file := range diffTree.Files {
 		item := &WebDiffFileItem{FullName: file.HeadPath, DiffStatus: file.Status}
+		if file.BasePath != file.HeadPath {
+			item.OldFullName = file.BasePath
+		}
 		item.IsViewed = filesViewedState[item.FullName] == pull_model.Viewed
 		item.NameHash = git.HashFilePathForWebUI(item.FullName)
 		item.FileIcon = fileicon.RenderEntryIconHTML(renderedIconPool, &fileicon.EntryInfo{BaseName: path.Base(file.HeadPath), EntryMode: file.HeadMode})

routers/web/repo/treelist_test.go

@@ -28,6 +28,12 @@ func TestTransformDiffTreeForWeb(t *testing.T) {
 			HeadPath: "file1",
 			HeadMode: git.EntryModeBlob,
 		},
+		{
+			Status:   "renamed",
+			BasePath: "file2-old",
+			HeadPath: "file2",
+			HeadMode: git.EntryModeBlob,
+		},
 	}}, map[string]pull_model.ViewedState{
 		"dir-a/dir-a-x/file-deep": pull_model.Viewed,
 	})
@@ -62,6 +68,15 @@ func TestTransformDiffTreeForWeb(t *testing.T) {
 					DiffStatus:  "added",
 					FileIcon:    mockIconForFile(`svg-mfi-file`),
 				},
+				{
+					EntryMode:   "",
+					DisplayName: "file2",
+					FullName:    "file2",
+					OldFullName: "file2-old",
+					NameHash:    "cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523",
+					DiffStatus:  "renamed",
+					FileIcon:    mockIconForFile(`svg-mfi-file`),
+				},
 			},
 		},
 	}, ret)