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>
2026-08-24 08:01:42 +00:00 · 2026-08-23 18:31:22 +02:00
parent 4852091e85
commit 2bcf950b78
28 changed files with 914 additions and 133 deletions
--- a/options/locale/locale_en-US.json
+++ b/options/locale/locale_en-US.json
@@ -2597,9 +2597,9 @@
  "repo.diff.file_byte_size": "Size",
  "repo.diff.file_suppressed": "File diff suppressed because it is too large",
  "repo.diff.file_suppressed_line_too_long": "File diff suppressed because one or more lines are too long",
-  "repo.diff.too_many_files": "Some files were not shown because too many files have changed in this diff",
-  "repo.diff.show_more": "Show More",
-  "repo.diff.load": "Load Diff",
+  "repo.diff.too_many_files": "Loaded %[1]d of %[2]d files, more files were not shown because too many files have changed in this diff.",
+  "repo.diff.show_more": "Show more",
+  "repo.diff.load": "Load diff",
  "repo.diff.generated": "Generated",
  "repo.diff.vendored": "Vendored",
  "repo.diff.comment.add_line_comment": "Add line comment",
@@ -2627,6 +2627,15 @@
  "repo.diff.has_escaped": "This line has hidden Unicode characters",
  "repo.diff.show_file_tree": "Show file tree",
  "repo.diff.hide_file_tree": "Hide file tree",
+  "repo.diff.filter_files": "Filter files…",
+  "repo.diff.filter_files_clear": "Clear filter",
+  "repo.diff.filter_by_file_extension": "Filter by file extension",
+  "repo.diff.file_extensions": "File extensions",
+  "repo.diff.no_file_extension": "No extension",
+  "repo.diff.dotfile_extension": "Dotfiles",
+  "repo.diff.all_file_extensions": "All extensions",
+  "repo.diff.no_files_matched": "No files matched your search",
+  "repo.diff.show_more_matching": "Show more - %[1]d matching below",
  "repo.diff.submodule_added": "Submodule %[1]s added at %[2]s",
  "repo.diff.submodule_deleted": "Submodule %[1]s deleted from %[2]s",
  "repo.diff.submodule_updated": "Submodule %[1]s updated: %[2]s",
--- a/routers/web/repo/treelist.go
+++ b/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})
--- a/routers/web/repo/treelist_test.go
+++ b/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)
--- a/templates/repo/diff/box.tmpl
+++ b/templates/repo/diff/box.tmpl
@@ -35,7 +35,9 @@
 			{{template "repo/diff/whitespace_dropdown" .}}
 			{{template "repo/diff/options_dropdown" .}}
 			{{if .PageIsPullFiles}}
-				<div id="diff-commit-select" data-merge-base="{{$.CompareInfo.CompareBase}}" data-issuelink="{{$.Issue.Link}}" data-queryparams="?style={{if $.IsSplitStyle}}split{{else}}unified{{end}}&whitespace={{$.WhitespaceBehavior}}&show-outdated={{$.ShowOutdatedComments}}" data-filter_changes_by_commit="{{ctx.Locale.Tr "repo.pulls.filter_changes_by_commit"}}">
+				<div id="diff-commit-select" data-merge-base="{{$.CompareInfo.CompareBase}}" data-issuelink="{{$.Issue.Link}}"
+					data-queryparams="?style={{if $.IsSplitStyle}}split{{else}}unified{{end}}&whitespace={{$.WhitespaceBehavior}}&show-outdated={{$.ShowOutdatedComments}}"
+					data-text-filter-changes-by-commit="{{ctx.Locale.Tr "repo.pulls.filter_changes_by_commit"}}">
 					{{/* the following will be replaced by vue component, but this avoids any loading artifacts till the vue component is initialized */}}
 					<div class="ui jump dropdown tiny basic button custom">
 						{{svg "octicon-git-commit"}}
@@ -61,7 +63,15 @@
 	<div id="diff-container">
 		{{if $showFileTree}}
 			{{$.FileIconPoolHTML}}
-			<div id="diff-file-tree" class="tw-hidden not-mobile"></div>
+			<div id="diff-file-tree" class="tw-hidden not-mobile" data-locale="{{JsonUtils.EncodeToString (dict
+				"filterFiles" (ctx.Locale.Tr "repo.diff.filter_files")
+				"filterFilesClear" (ctx.Locale.Tr "repo.diff.filter_files_clear")
+				"filterByFileExtension" (ctx.Locale.Tr "repo.diff.filter_by_file_extension")
+				"fileExtensions" (ctx.Locale.Tr "repo.diff.file_extensions")
+				"noFileExtension" (ctx.Locale.Tr "repo.diff.no_file_extension")
+				"dotfileExtension" (ctx.Locale.Tr "repo.diff.dotfile_extension")
+				"allFileExtensions" (ctx.Locale.Tr "repo.diff.all_file_extensions")
+			)}}"></div>
 			<script nonce="{{ctx.CspScriptNonce}}">
 				if (diffTreeVisible) document.getElementById('diff-file-tree').classList.remove('tw-hidden');
 			</script>
@@ -69,7 +79,13 @@
 		{{if .DiffNotAvailable}}
 			<h4>{{ctx.Locale.Tr "repo.diff.data_not_available"}}</h4>
 		{{else}}
-			<div id="diff-file-boxes" class="sixteen wide column">
+			<div id="diff-boxes-column">
+				{{if $showFileTree}}
+					<div id="diff-no-matches" class="empty-placeholder tw-hidden">
+						<h2>{{ctx.Locale.Tr "repo.diff.no_files_matched"}}</h2>
+					</div>
+				{{end}}
+				<div id="diff-file-boxes">
 				{{range $i, $file := .Diff.Files}}
 					{{/*notice: the index of Diff.Files should not be used for element ID, because the index will be restarted from 0 when doing load-more for PRs with a lot of files*/}}
 					{{$isImage:= $file.IsBlobTypeImage}}
@@ -206,13 +222,17 @@
 				{{end}}

 				{{if .Diff.IsIncomplete}}
-					<div class="diff-file-box file-content tw-mt-2" id="diff-incomplete">
-						<h4 class="ui top attached header tw-font-normal flex-left-right">
-							{{ctx.Locale.Tr "repo.diff.too_many_files"}}
-							<a class="ui basic tiny button" id="diff-show-more-files" data-global-click="diffLoadMoreFiles" data-href="?skip-to={{.Diff.End}}&file-only=true">{{ctx.Locale.Tr "repo.diff.show_more"}}</a>
-						</h4>
+					<div class="ui segment flex-left-right" id="diff-incomplete">
+						<span id="diff-load-progress" class="tw-text-text-light-2" data-text-too-many-files="{{ctx.Locale.Tr "repo.diff.too_many_files"}}">
+							{{ctx.Locale.Tr "repo.diff.too_many_files" (len .Diff.Files) .DiffShortStat.NumFiles}}
+						</span>
+						<a class="ui basic tiny button" id="diff-show-more-files" data-global-click="diffLoadMoreFiles" data-href="?skip-to={{.Diff.End}}&file-only=true"
+							data-text-default="{{ctx.Locale.Tr "repo.diff.show_more"}}"
+							data-text-matching="{{ctx.Locale.Tr "repo.diff.show_more_matching"}}"
+						>{{ctx.Locale.Tr "repo.diff.show_more"}}</a>
 					</div>
 				{{end}}
+				</div>
 			</div>
 		{{end}}
 	</div>
--- a/tests/e2e/external-render.test.ts
+++ b/tests/e2e/external-render.test.ts
@@ -1,6 +1,6 @@
 import {env} from 'node:process';
 import {expect, test} from '@playwright/test';
-import {login, apiCreateRepo, apiCreateFile, assertFlushWithParent, assertNoJsError, randomString} from './utils.ts';
+import {login, apiCreateRepo, apiCreateFiles, assertFlushWithParent, assertNoJsError, randomString} from './utils.ts';

 test('external file', async ({page, request}) => {
  const repoName = `e2e-external-render-${randomString(8)}`;
@@ -9,7 +9,7 @@ test('external file', async ({page, request}) => {
    apiCreateRepo(request, {name: repoName}),
    login(page),
  ]);
-  await apiCreateFile(request, owner, repoName, 'test.external', '<p>rendered content</p>');
+  await apiCreateFiles(request, owner, repoName, [{path: 'test.external', content: '<p>rendered content</p>'}]);
  await page.goto(`/${owner}/${repoName}/src/branch/main/test.external`);
  const iframe = page.locator('iframe.external-render-iframe');
  await expect(iframe).toBeVisible();
@@ -34,7 +34,7 @@ test('openapi file', async ({page, request}) => {
    paths: {'/pets': {get: {responses: {'200': {description: 'OK', content: {'application/json': {schema: {$ref: '#/components/schemas/Pet'}}}}}}}},
    components: {schemas: {Pet: {type: 'object', properties: {children: {type: 'array', items: {$ref: '#/components/schemas/Pet'}}}}}},
  });
-  await apiCreateFile(request, owner, repoName, 'openapi.json', spec);
+  await apiCreateFiles(request, owner, repoName, [{path: 'openapi.json', content: spec}]);
  await page.goto(`/${owner}/${repoName}/src/branch/main/openapi.json`);
  const iframe = page.locator('iframe.external-render-iframe');
  await expect(iframe).toBeVisible();
--- a/tests/e2e/file-view-render.test.ts
+++ b/tests/e2e/file-view-render.test.ts
@@ -1,6 +1,6 @@
 import {env} from 'node:process';
 import {expect, test} from '@playwright/test';
-import {apiCreateRepo, apiCreateFile, assertFlushWithParent, assertNoJsError, login, randomString} from './utils.ts';
+import {apiCreateRepo, apiCreateFiles, assertFlushWithParent, assertNoJsError, login, randomString} from './utils.ts';

 test('3d model file', async ({page, request, browserName}) => {
  test.skip(browserName === 'firefox', 'unclear firefox-only CI-only failure'); // eslint-disable-line playwright/no-skipped-test -- conditional skip, the reason is in the message
@@ -8,7 +8,7 @@ test('3d model file', async ({page, request, browserName}) => {
  const owner = env.GITEA_TEST_E2E_USER;
  await apiCreateRepo(request, {name: repoName});
  const stl = 'solid test\nfacet normal 0 0 1\nouter loop\nvertex 0 0 0\nvertex 1 0 0\nvertex 0 1 0\nendloop\nendfacet\nendsolid test\n';
-  await apiCreateFile(request, owner, repoName, 'test.stl', stl);
+  await apiCreateFiles(request, owner, repoName, [{path: 'test.stl', content: stl}]);
  await page.goto(`/${owner}/${repoName}/src/branch/main/test.stl?display=rendered`);
  const iframe = page.locator('iframe.external-render-iframe');
  await expect(iframe).toBeVisible();
@@ -31,7 +31,7 @@ test('pdf file', async ({page, request}) => {
  const repoName = `e2e-pdf-render-${randomString(8)}`;
  const owner = env.GITEA_TEST_E2E_USER;
  await apiCreateRepo(request, {name: repoName});
-  await apiCreateFile(request, owner, repoName, 'test.pdf', '%PDF-1.0\n%%EOF\n');
+  await apiCreateFiles(request, owner, repoName, [{path: 'test.pdf', content: '%PDF-1.0\n%%EOF\n'}]);
  await page.goto(`/${owner}/${repoName}/src/branch/main/test.pdf`);
  const container = page.locator('.file-view-render-container');
  await expect(container).toHaveAttribute('data-render-name', 'pdf-viewer');
@@ -47,7 +47,7 @@ test('asciicast file', async ({page, request}) => {
  await Promise.all([apiCreateRepo(request, {name: repoName, autoInit: false}), login(page)]);
  const cast = '{"version": 2, "width": 80, "height": 24}\n[0.0, "o", "test-content"]\n';
  // on an empty repo, apiCreateFile with newBranch creates that branch as the initial commit
-  await apiCreateFile(request, owner, repoName, 'test.cast', cast, {newBranch: branch});
+  await apiCreateFiles(request, owner, repoName, [{path: 'test.cast', content: cast}], {newBranch: branch});
  await page.goto(`/${owner}/${repoName}/src/branch/${branchEnc}/test.cast`);
  const iframe = page.locator('iframe.external-render-iframe');
  const frame = iframe.contentFrame();
--- a/tests/e2e/pr-create.test.ts
+++ b/tests/e2e/pr-create.test.ts
@@ -1,13 +1,13 @@
 import {env} from 'node:process';
 import {test, expect} from '@playwright/test';
-import {login, apiCreateRepo, apiCreateFile, randomString} from './utils.ts';
+import {login, apiCreateRepo, apiCreateFiles, randomString} from './utils.ts';

 test('create a pull request from the compare page', async ({page, request}) => {
  const repoName = `e2e-pr-create-${randomString(8)}`;
  const owner = env.GITEA_TEST_E2E_USER;
  await apiCreateRepo(request, {name: repoName});
  await Promise.all([
-    apiCreateFile(request, owner, repoName, 'feat.txt', 'feature content\n', {branch: 'main', newBranch: 'feat'}),
+    apiCreateFiles(request, owner, repoName, [{path: 'feat.txt', content: 'feature content\n'}], {branch: 'main', newBranch: 'feat'}),
    login(page),
  ]);
  // expand=1 renders the PR form directly, skipping the "New Pull Request" toggle click
--- a/tests/e2e/pr-diff-filter.test.ts
+++ b/tests/e2e/pr-diff-filter.test.ts
@@ -0,0 +1,87 @@
+import {test, expect} from '@playwright/test';
+import {apiCreateFiles, apiCreatePR, apiCreateRepo, apiCreateUser, apiUserHeaders, loginUser, randomString} from './utils.ts';
+
+test('diff sidebar filtering', async ({page, request}) => {
+  const user = `df-${randomString(8)}`;
+  await apiCreateUser(request, user);
+  const headers = apiUserHeaders(user);
+  const repo = `e2e-difffilter-${randomString(8)}`;
+  await apiCreateRepo(request, {name: repo, headers});
+
+  await apiCreateFiles(request, user, repo, [
+    {path: 'src/a.ts', content: 'a\n'},
+    {path: 'src/b.ts', content: 'b\n'},
+    {path: 'src/.eslintrc', content: 'e\n'}, // dotfiles count as "No extension"
+    {path: 'styles/x.css', content: 'x\n'},
+    {path: 'docs/intro.md', content: 'r\n'},
+    {path: 'Makefile', content: 'm\n'},
+  ], {branch: 'main', newBranch: 'feat', headers});
+  const prIndex = await apiCreatePR(request, user, repo, 'feat', 'main', 'diff filter test', {headers});
+
+  await loginUser(page, user);
+  await page.goto(`/${user}/${repo}/pulls/${prIndex}/files`);
+
+  const tree = page.locator('#diff-file-tree');
+  const items = tree.locator('.item-file');
+  const search = tree.getByRole('textbox');
+  const filterTrigger = tree.getByRole('button', {name: 'Filter by file extension'});
+
+  // every PR file is listed
+  await expect(items).toHaveCount(6);
+
+  // sidebar leaves the diff column the bulk of the viewport
+  const boxesWidth = (await page.locator('#diff-file-boxes').boundingBox())!.width;
+  const treeWidth = (await tree.boundingBox())!.width;
+  expect(boxesWidth).toBeGreaterThan(treeWidth * 2);
+
+  // search filters tree and file boxes
+  await search.fill('a.ts');
+  await expect(items).toHaveText([/a\.ts/]);
+  await expect(page.locator('.diff-file-box[data-new-filename="src/a.ts"]')).toBeVisible();
+
+  await tree.getByRole('button', {name: 'Clear filter'}).click();
+  await expect(items).toHaveCount(6);
+
+  // empty-result placeholder
+  await search.fill('zzz-no-such-file');
+  await expect(page.locator('#diff-no-matches')).toBeVisible();
+  await search.fill('');
+
+  // extensions sort alphabetically, then dotfiles, then files without extension
+  await filterTrigger.click();
+  const extItems = page.getByRole('menuitemcheckbox');
+  await expect(extItems).toHaveText(['.css1', '.md1', '.ts2', 'Dotfiles1', 'No extension1', 'All extensions']);
+
+  // deselecting .ts leaves the other extensions
+  const allExtensions = page.getByRole('menuitemcheckbox', {name: 'All extensions'});
+  await page.getByRole('menuitemcheckbox', {name: '.ts'}).click();
+  await expect(items).toHaveCount(4);
+  await expect(filterTrigger).toHaveClass(/\bindicator-dot\b/);
+  await expect(allExtensions).toHaveAttribute('aria-checked', 'false');
+
+  // "All extensions" cycles through select all, select none and back
+  await allExtensions.click();
+  await expect(allExtensions).toHaveAttribute('aria-checked', 'true');
+  await expect(items).toHaveCount(6);
+
+  await allExtensions.click();
+  await expect(items).toHaveCount(0);
+
+  await allExtensions.click();
+  await expect(items).toHaveCount(6);
+  await expect(filterTrigger).not.toHaveClass(/\bindicator-dot\b/);
+
+  // the extension filter lives in the URL and survives a reload
+  await page.getByRole('menuitemcheckbox', {name: '.ts'}).click();
+  await expect(page).toHaveURL(/file-filters/);
+  await page.reload();
+  await expect(items).toHaveCount(4);
+  await expect(filterTrigger).toHaveClass(/\bindicator-dot\b/);
+
+  // hiding the file tree drops the filter
+  await expect(page.locator('.diff-file-box[data-new-filename="src/a.ts"]')).toBeHidden();
+  await filterTrigger.click();
+  await page.locator('.diff-toggle-file-tree-button').click();
+  await expect(tree).toBeHidden();
+  await expect(page.locator('.diff-file-box[data-new-filename="src/a.ts"]')).toBeVisible();
+});
--- a/tests/e2e/pr-review.test.ts
+++ b/tests/e2e/pr-review.test.ts
@@ -1,5 +1,5 @@
 import {test, expect} from '@playwright/test';
-import {apiCreateFile, apiCreatePR, apiCreateRepo, apiCreateReview, apiCreateUser, apiUserHeaders, loginUser, randomString} from './utils.ts';
+import {apiCreateFiles, apiCreatePR, apiCreateRepo, apiCreateReview, apiCreateUser, apiUserHeaders, loginUser, randomString} from './utils.ts';

 test('pr review flow', async ({page, request}) => {
  const poster = `rv-poster-${randomString(8)}`;
@@ -8,7 +8,7 @@ test('pr review flow', async ({page, request}) => {
  const posterHeaders = apiUserHeaders(poster);
  const repoName = `e2e-prreview-${randomString(8)}`;
  await apiCreateRepo(request, {name: repoName, headers: posterHeaders});
-  await apiCreateFile(request, poster, repoName, 'added.txt', 'new content\n', {branch: 'main', newBranch: 'feat'});
+  await apiCreateFiles(request, poster, repoName, [{path: 'added.txt', content: 'new content\n'}], {branch: 'main', newBranch: 'feat', headers: posterHeaders});
  const prIndex = await apiCreatePR(request, poster, repoName, 'feat', 'main', 'review test', {headers: posterHeaders});

  // reviewer seeds an inline comment via API so the poster's UI reply exercises the reply-to-review path (#35994)
--- a/tests/e2e/pull-merge-box.test.ts
+++ b/tests/e2e/pull-merge-box.test.ts
@@ -1,6 +1,6 @@
 import {env} from 'node:process';
 import {test, expect} from '@playwright/test';
-import {apiCreateFile, apiCreatePR, apiCreateRepo, assertNoJsError, login, randomString} from './utils.ts';
+import {apiCreateFiles, apiCreatePR, apiCreateRepo, assertNoJsError, login, randomString} from './utils.ts';

 const owner = env.GITEA_TEST_E2E_USER;

@@ -8,7 +8,7 @@ test('merge box merges a pull request', async ({page, request}) => {
  const repo = `e2e-merge-box-${randomString(8)}`;
  const createPR = (async () => {
    await apiCreateRepo(request, {name: repo});
-    await apiCreateFile(request, owner, repo, 'feat.txt', 'feature\n', {branch: 'main', newBranch: 'feat'});
+    await apiCreateFiles(request, owner, repo, [{path: 'feat.txt', content: 'feature\n'}], {branch: 'main', newBranch: 'feat'});
    return apiCreatePR(request, owner, repo, 'feat', 'main', 'merge box test');
  })();
  const [index] = await Promise.all([createPR, login(page)]);
--- a/tests/e2e/utils.ts
+++ b/tests/e2e/utils.ts
@@ -12,8 +12,6 @@ export function randomString(length: number): string {
  return result;
 }

-export const timeoutFactor = Number(env.GITEA_TEST_E2E_TIMEOUT_FACTOR) || 1;
-
 export function baseUrl() {
  return env.GITEA_TEST_E2E_URL?.replace(/\/$/g, '');
 }
@@ -67,6 +65,17 @@ export async function apiStartStopwatch(requestContext: APIRequestContext, owner
  }), 'apiStartStopwatch');
 }

+/** Commit one or more files in a single API call. */
+export async function apiCreateFiles(requestContext: APIRequestContext, owner: string, repo: string, files: Array<{path: string; content: string}>, {branch, newBranch, headers}: {branch?: string; newBranch?: string; headers?: Record<string, string>} = {}) {
+  await apiRetry(() => requestContext.post(`${baseUrl()}/api/v1/repos/${owner}/${repo}/contents`, {
+    headers: headers || apiHeaders(),
+    data: {
+      branch, new_branch: newBranch,
+      files: files.map((file) => ({operation: 'create', path: file.path, content: Buffer.from(file.content, 'utf8').toString('base64')})),
+    },
+  }), 'apiCreateFiles');
+}
+
 export async function apiCancelStopwatch(requestContext: APIRequestContext, owner: string, repo: string, issueIndex: number, {headers}: {headers?: Record<string, string>} = {}) {
  await apiRetry(() => requestContext.delete(`${baseUrl()}/api/v1/repos/${owner}/${repo}/issues/${issueIndex}/stopwatch/delete`, {
    headers: headers || apiHeaders(),
@@ -80,20 +89,6 @@ export async function apiCloseIssue(requestContext: APIRequestContext, owner: st
  }), 'apiCloseIssue');
 }

-export async function apiCreateFile(requestContext: APIRequestContext, owner: string, repo: string, filepath: string, content: string, {branch, newBranch, message}: {branch?: string; newBranch?: string; message?: string} = {}) {
-  await apiRetry(() => requestContext.post(`${baseUrl()}/api/v1/repos/${owner}/${repo}/contents/${filepath}`, {
-    headers: apiHeaders(),
-    data: {content: Buffer.from(content, 'utf8').toString('base64'), branch, new_branch: newBranch, message},
-  }), 'apiCreateFile');
-}
-
-export async function apiCreateBranch(requestContext: APIRequestContext, owner: string, repo: string, newBranch: string) {
-  await apiRetry(() => requestContext.post(`${baseUrl()}/api/v1/repos/${owner}/${repo}/branches`, {
-    headers: apiHeaders(),
-    data: {new_branch_name: newBranch},
-  }), 'apiCreateBranch');
-}
-
 /** Create a PR via API. Returns the PR index for subsequent operations. */
 export async function apiCreatePR(requestContext: APIRequestContext, owner: string, repo: string, head: string, base: string, title: string, {headers}: {headers?: Record<string, string>} = {}): Promise<number> {
  let prIndex = 0;
--- a/web_src/css/helpers.css
+++ b/web_src/css/helpers.css
@@ -30,6 +30,24 @@ Gitea's private styles use `g-` prefix.
 .interact-bg:hover { background: var(--color-hover) !important; }
 .interact-bg:active { background: var(--color-active) !important; }

+/* primary-color dot centered on the top-right corner of the element */
+.indicator-dot {
+  position: relative;
+}
+
+.indicator-dot::after {
+  content: "";
+  position: absolute;
+  top: 0;
+  right: 0;
+  width: 9px;
+  height: 9px;
+  border-radius: 50%;
+  background: var(--color-primary);
+  border: 1px solid var(--color-secondary);
+  transform: translate(50%, -50%);
+}
+
@media (max-width: 767.98px) {
  /* double selector so it wins over .tw-flex (old .gt-df) etc */
  .not-mobile.not-mobile {
--- a/web_src/css/modules/tippy.css
+++ b/web_src/css/modules/tippy.css
@@ -14,6 +14,18 @@
  max-width: calc(100vw - 32px);
 }

+/* opt-in via createTippy's "limitSizeToViewport" */
+[data-tippy-limit-size] .tippy-box {
+  display: flex;
+  flex-direction: column;
+  max-width: var(--tippy-max-width, none);
+  max-height: var(--tippy-max-height, none);
+}
+
+[data-tippy-limit-size] .tippy-content {
+  overflow: auto;
+}
+
 .tippy-box {
  position: relative;
  background-color: var(--color-menu);
@@ -91,7 +103,7 @@
  background: var(--color-hover);
 }

-.tippy-box[data-theme="menu"] .item:focus {
+.tippy-box[data-theme="menu"] .item:focus-visible {
  background: var(--color-hover);
 }

@@ -99,6 +111,10 @@
  background: var(--color-active);
 }

+.tippy-box[data-theme="menu"] .divider {
+  margin: 4px 0; /* fit the menu's vertical padding */
+}
+
 /* box-with-header theme to look like .ui.attached.segment. can contain .ui.attached.header */

 .tippy-box[data-theme="box-with-header"] {
--- a/web_src/css/repo.css
+++ b/web_src/css/repo.css
@@ -1549,27 +1549,38 @@ tbody.commit-list {

 #diff-container {
  display: flex;
+  padding-top: 4px; /* for box-shadow from .diff-file-box */
  gap: var(--page-spacing);
 }

-#diff-file-boxes {
+#diff-boxes-column {
  flex: 1;
-  max-width: 100%;
+  min-width: 0;
+}
+
+#diff-file-boxes {
  display: flex;
  flex-direction: column;
  gap: 8px;
 }

 #diff-file-tree {
-  flex: 0 0 20%;
-  max-width: 380px;
+  flex: 0 0 256px;
+  min-width: 0;
  line-height: inherit;
  position: sticky;
  padding-top: 0;
  top: 47px;
  max-height: calc(100vh - 47px);
  height: 100%;
-  overflow-y: auto;
+  display: flex;
+  flex-direction: column;
+}
+
+@media (min-width: 1201px) {
+  #diff-file-tree {
+    flex-basis: 320px;
+  }
 }

 .ui.message.unicode-escape-prompt {
--- a/web_src/js/components/DiffCommitSelector.vue
+++ b/web_src/js/components/DiffCommitSelector.vue
@@ -33,7 +33,7 @@ const uniqueIdShowAll = generateElemId('diff-commit-selector-show-all-');

 const menuVisible = shallowRef(false);
 const isLoading = shallowRef(false);
-const locale = shallowRef<Record<string, string>>({filter_changes_by_commit: elMount.getAttribute('data-filter_changes_by_commit')!});
+const locale = shallowRef<Record<string, string>>({filter_changes_by_commit: elMount.getAttribute('data-text-filter-changes-by-commit')!});
 const commits = ref<Array<Commit>>([]); // deep, the commit objects are mutated in place
 const hoverActivated = shallowRef(false);
 const lastReviewCommitSha = shallowRef<string | null>(null);
--- a/web_src/js/components/DiffFileExtensionFilter.vue
+++ b/web_src/js/components/DiffFileExtensionFilter.vue
@@ -0,0 +1,168 @@
+<script lang="ts" setup>
+import {computed, onMounted, onUnmounted, useTemplateRef} from 'vue';
+import type {Instance} from 'tippy.js';
+import SvgIcon from './SvgIcon.vue';
+import type {SvgName} from '../svg.ts';
+import {createTippy} from '../modules/tippy.ts';
+import {diffTreeStore, extDotfile, getDiffTreeExtensionStats, type DiffExtensionFilterLocale} from '../modules/diff-file.ts';
+
+const props = defineProps<{locale: DiffExtensionFilterLocale}>();
+
+const store = diffTreeStore();
+const triggerEl = useTemplateRef<HTMLButtonElement>('triggerEl');
+const panelEl = useTemplateRef<HTMLDivElement>('panelEl');
+let tippyInstance: Instance;
+
+const allExtensions = computed(() => getDiffTreeExtensionStats(store));
+const isFiltering = computed(() => store.activeExtensions !== 'all' || Boolean(store.filenameFilterQuery));
+const allIcon = computed<SvgName | null>(() => {
+  if (store.activeExtensions === 'all') return 'octicon-check';
+  return store.activeExtensions.length ? 'octicon-dash' : null;
+});
+
+function isChecked(ext: string): boolean {
+  return store.activeExtensions === 'all' || store.activeExtensions.includes(ext);
+}
+
+function extLabel(ext: string): string {
+  if (ext === extDotfile) return props.locale.dotfileExtension;
+  return ext || props.locale.noFileExtension;
+}
+
+function toggleExt(ext: string) {
+  const all = allExtensions.value.map((e) => e.ext);
+  const next = new Set(store.activeExtensions === 'all' ? all : store.activeExtensions);
+  if (next.has(ext)) next.delete(ext); else next.add(ext);
+  store.activeExtensions = next.size === all.length ? 'all' : Array.from(next);
+}
+
+function toggleAll() {
+  store.activeExtensions = store.activeExtensions === 'all' ? [] : 'all';
+}
+
+function onKeyDown(e: KeyboardEvent) {
+  if (e.key === 'Escape') tippyInstance.hide();
+}
+
+onMounted(() => {
+  tippyInstance = createTippy(triggerEl.value!, {
+    content: panelEl.value!,
+    trigger: 'click',
+    interactive: true,
+    hideOnClick: true,
+    placement: 'bottom-end',
+    theme: 'menu',
+    arrow: false,
+    limitSizeToViewport: {vertical: true},
+    onShow: () => document.addEventListener('keydown', onKeyDown),
+    onHide: () => document.removeEventListener('keydown', onKeyDown),
+  });
+});
+
+onUnmounted(() => {
+  tippyInstance.destroy();
+});
+</script>
+
+<template>
+  <button
+    ref="triggerEl"
+    type="button"
+    class="diff-ext-filter-trigger"
+    :class="{'indicator-dot': isFiltering}"
+    :aria-label="props.locale.filterByFileExtension"
+  >
+    <SvgIcon name="octicon-filter"/>
+  </button>
+  <div ref="panelEl" class="tippy-target">
+    <div class="diff-ext-filter-menu" role="menu" :aria-label="props.locale.fileExtensions">
+      <div class="diff-ext-filter-header">{{ props.locale.fileExtensions }}</div>
+      <div class="diff-ext-filter-list">
+        <button
+          v-for="ext in allExtensions" :key="ext.ext"
+          type="button" class="item" role="menuitemcheckbox"
+          :aria-checked="isChecked(ext.ext)" @click="toggleExt(ext.ext)"
+        >
+          <span class="diff-ext-filter-check">
+            <SvgIcon v-if="isChecked(ext.ext)" name="octicon-check"/>
+          </span>
+          <span class="gt-ellipsis">{{ extLabel(ext.ext) }}</span>
+          <span class="diff-ext-filter-count">{{ ext.count }}</span>
+        </button>
+      </div>
+      <div class="divider"/>
+      <button
+        type="button" class="item" role="menuitemcheckbox"
+        :aria-checked="store.activeExtensions === 'all'" @click="toggleAll"
+      >
+        <span class="diff-ext-filter-check">
+          <SvgIcon v-if="allIcon" :name="allIcon"/>
+        </span>
+        <span class="gt-ellipsis">{{ props.locale.allFileExtensions }}</span>
+      </button>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.diff-ext-filter-menu {
+  min-width: 192px;
+  max-width: 320px;
+}
+
+.diff-ext-filter-header {
+  padding: 6px 16px;
+  color: var(--color-text-light-2);
+  font-size: 12px;
+  font-weight: var(--font-weight-semibold);
+}
+
+.diff-ext-filter-list {
+  display: flex;
+  flex-direction: column;
+}
+
+.diff-ext-filter-menu .item {
+  width: auto; /* buttons are shrink-to-fit, the flex column parent stretches them */
+  margin: 0 4px; /* matches the menu's vertical padding so the inset is even on all sides */
+  padding: 6px 12px;
+  gap: 8px;
+  border: none;
+  border-radius: var(--border-radius-medium);
+  font: inherit;
+  text-align: left;
+}
+
+.diff-ext-filter-check {
+  display: flex;
+  flex: 0 0 16px;
+  color: var(--color-text-light-2);
+}
+
+.diff-ext-filter-count {
+  margin-left: auto;
+  padding: 2px 6px;
+  border-radius: var(--border-radius-full);
+  background: var(--color-label-bg);
+  font-size: 12px;
+  font-weight: var(--font-weight-semibold);
+  line-height: 12px;
+}
+
+.diff-ext-filter-trigger {
+  height: 32px;
+  width: 32px;
+  padding: 0;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius-medium);
+  background: var(--color-button);
+  color: var(--color-text-light-2);
+}
+
+.diff-ext-filter-trigger:hover {
+  background: var(--color-hover);
+}
+</style>
--- a/web_src/js/components/DiffFileTree.vue
+++ b/web_src/js/components/DiffFileTree.vue
@@ -1,20 +1,33 @@
 <script lang="ts" setup>
+import SvgIcon from './SvgIcon.vue';
 import DiffFileTreeItem from './DiffFileTreeItem.vue';
-import {toggleElem} from '../utils/dom.ts';
-import {diffTreeStore} from '../modules/diff-file.ts';
+import DiffFileExtensionFilter from './DiffFileExtensionFilter.vue';
+import {onInputDebounce, toggleElem} from '../utils/dom.ts';
+import {diffTreeStore, filterDiffTree, applyFiltersToFileBoxes, extensionFilterToUrl, type DiffFileTreeLocale} from '../modules/diff-file.ts';
 import {setFileFolding} from '../features/file-fold.ts';
-import {onMounted, onUnmounted} from 'vue';
+import {onMounted, onUnmounted, computed, watch} from 'vue';
 import {localUserSettings} from '../modules/user-settings.ts';

 const LOCAL_STORAGE_KEY = 'diff_file_tree_visible';

+const props = defineProps<{locale: DiffFileTreeLocale}>();
+
 const store = diffTreeStore();

+const visibleTreeItems = computed(() => filterDiffTree(store)?.Children ?? []);
+
+watch(() => store.filenameFilterQuery, onInputDebounce(() => applyFiltersToFileBoxes(store)));
+watch(() => store.activeExtensions, () => {
+  applyFiltersToFileBoxes(store);
+  window.history.replaceState(null, '', extensionFilterToUrl(store.activeExtensions, window.location.href));
+});
+
 onMounted(() => {
  // Default to true if unset
  store.fileTreeIsVisible = localUserSettings.getBoolean(LOCAL_STORAGE_KEY, true);
+  // while the tree is hidden there is no control to clear a filter restored from the URL
+  if (store.fileTreeIsVisible) applyFiltersToFileBoxes(store); else store.activeExtensions = 'all';
  document.querySelector('.diff-toggle-file-tree-button')!.addEventListener('click', toggleVisibility);
-
  hashChangeListener();
  window.addEventListener('hashchange', hashChangeListener);
 });
@@ -44,6 +57,11 @@ function toggleVisibility() {

 function updateVisibility(visible: boolean) {
  store.fileTreeIsVisible = visible;
+  if (!visible) {
+    store.filenameFilterQuery = '';
+    store.activeExtensions = 'all';
+    applyFiltersToFileBoxes(store);
+  }
  localUserSettings.setBoolean(LOCAL_STORAGE_KEY, store.fileTreeIsVisible);
  updateState(store.fileTreeIsVisible);
 }
@@ -62,16 +80,110 @@ function updateState(visible: boolean) {

 <template>
  <!-- only render the tree if we're visible. in many cases this is something that doesn't change very often -->
-  <div v-if="store.fileTreeIsVisible" class="diff-file-tree-items">
-    <DiffFileTreeItem v-for="item in store.diffFileTree.TreeRoot.Children" :key="item.FullName" :item="item"/>
+  <div v-if="store.fileTreeIsVisible" class="diff-file-tree-wrapper">
+    <div class="diff-file-tree-search-row">
+      <div class="diff-file-search-wrapper">
+        <SvgIcon name="octicon-search" :size="14" class="diff-file-search-icon"/>
+        <input
+          type="text"
+          v-model="store.filenameFilterQuery"
+          class="diff-file-search-input"
+          :placeholder="props.locale.filterFiles"
+          :aria-label="props.locale.filterFiles"
+        >
+        <button
+          v-if="store.filenameFilterQuery"
+          type="button"
+          class="diff-file-search-clear"
+          @click="store.filenameFilterQuery = ''"
+          :aria-label="props.locale.filterFilesClear"
+        >
+          <SvgIcon name="octicon-x" :size="14"/>
+        </button>
+      </div>
+      <DiffFileExtensionFilter :locale="props.locale"/>
+    </div>
+    <div class="diff-file-tree-items">
+      <DiffFileTreeItem v-for="item in visibleTreeItems" :key="item.FullName" :item="item"/>
+    </div>
  </div>
 </template>

 <style scoped>
+.diff-file-tree-wrapper {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  margin-right: .5rem;
+  flex: 1;
+  min-height: 0;
+}
+
+.diff-file-tree-search-row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding-top: 1px; /* match .diff-file-box's top border so this row aligns with .diff-file-header */
+  padding-bottom: 0.25rem;
+}
+
+.diff-file-search-wrapper {
+  flex: 1;
+  min-width: 0;
+  position: relative;
+  display: flex;
+  align-items: center;
+}
+
+.diff-file-search-icon {
+  position: absolute;
+  left: 8px;
+  color: var(--color-text-light-2);
+  pointer-events: none;
+}
+
+.diff-file-search-input {
+  flex: 1;
+  min-width: 0;
+  height: 32px;
+  padding: 0 28px;
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius-medium);
+  background: var(--color-input-background);
+  color: var(--color-text);
+}
+
+.diff-file-search-input:focus {
+  outline: none;
+  border-color: var(--color-primary);
+}
+
+.diff-file-search-clear {
+  position: absolute;
+  right: 4px;
+  top: 0;
+  bottom: 0;
+  width: 20px;
+  background: none;
+  border: none;
+  color: var(--color-text-light);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  margin: auto 0;
+  padding: 0;
+}
+
+.diff-file-search-clear:hover {
+  color: var(--color-text);
+}
+
 .diff-file-tree-items {
  display: flex;
  flex-direction: column;
  gap: 1px;
-  margin-right: .5rem;
+  overflow-y: auto;
+  flex: 1;
+  min-height: 0;
 }
 </style>
--- a/web_src/js/components/DiffFileTreeItem.test.ts
+++ b/web_src/js/components/DiffFileTreeItem.test.ts
@@ -0,0 +1,23 @@
+import DiffFileTreeItem from './DiffFileTreeItem.vue';
+import {createApp, h} from 'vue';
+import type {DiffStatus, DiffTreeEntry} from '../modules/diff-file.ts';
+
+function renderItem(diffStatus: string): string {
+  const item: DiffTreeEntry = {
+    FullName: 'a.txt', OldFullName: '', DisplayName: 'a.txt', NameHash: 'hash',
+    DiffStatus: diffStatus as DiffStatus, EntryMode: '', IsViewed: false, Children: null, FileIcon: '',
+  };
+  const root = document.createElement('div');
+  createApp({render: () => h(DiffFileTreeItem, {item})}).mount(root);
+  return root.innerHTML;
+}
+
+test('DiffFileTreeItem diff status icon', () => {
+  window.config.pageData.DiffFileTree = {TreeRoot: {
+    FullName: '', OldFullName: '', DisplayName: '', NameHash: 'root',
+    DiffStatus: '', EntryMode: 'tree', IsViewed: false, Children: [], FileIcon: '',
+  }};
+  expect(renderItem('typechanged')).toContain('octicon-diff-modified');
+  // a status the frontend does not know must fall back instead of failing to render
+  expect(renderItem('something-new')).toContain('octicon-blocked');
+});
--- a/web_src/js/components/DiffFileTreeItem.vue
+++ b/web_src/js/components/DiffFileTreeItem.vue
@@ -11,18 +11,17 @@ const props = defineProps<{
 const store = diffTreeStore();
 const collapsed = shallowRef(props.item.IsViewed);

-function getIconForDiffStatus(pType: DiffStatus) {
-  const diffTypes: Record<DiffStatus, { name: SvgName, classes: Array<string> }> = {
-    '': {name: 'octicon-blocked', classes: ['tw-text-red']}, // unknown case
-    'added': {name: 'octicon-diff-added', classes: ['tw-text-green']},
-    'modified': {name: 'octicon-diff-modified', classes: ['tw-text-yellow']},
-    'deleted': {name: 'octicon-diff-removed', classes: ['tw-text-red']},
-    'renamed': {name: 'octicon-diff-renamed', classes: ['tw-text-teal']},
-    'copied': {name: 'octicon-diff-renamed', classes: ['tw-text-green']},
-    'typechange': {name: 'octicon-diff-modified', classes: ['tw-text-green']}, // there is no octicon for copied, so renamed should be ok
-  };
-  return diffTypes[pType] ?? diffTypes[''];
-}
+const diffStatusIcons: Record<DiffStatus, {name: SvgName, class: string}> = {
+  '': {name: 'octicon-blocked', class: 'tw-text-red'},
+  'added': {name: 'octicon-diff-added', class: 'tw-text-green'},
+  'modified': {name: 'octicon-diff-modified', class: 'tw-text-yellow'},
+  'deleted': {name: 'octicon-diff-removed', class: 'tw-text-red'},
+  'renamed': {name: 'octicon-diff-renamed', class: 'tw-text-teal'},
+  'copied': {name: 'octicon-diff-renamed', class: 'tw-text-green'}, // there is no octicon for copied, so renamed should be ok
+  'typechanged': {name: 'octicon-diff-modified', class: 'tw-text-green'},
+  'unmerged': {name: 'octicon-blocked', class: 'tw-text-red'},
+  'unknown': {name: 'octicon-blocked', class: 'tw-text-red'},
+};
 </script>

 <template>
@@ -36,7 +35,7 @@ function getIconForDiffStatus(pType: DiffStatus) {
    </div>

    <div v-show="!collapsed" class="sub-items">
-      <DiffFileTreeItem v-for="childItem in item.Children" :key="childItem.DisplayName" :item="childItem"/>
+      <DiffFileTreeItem v-for="childItem in item.Children!" :key="childItem.DisplayName" :item="childItem"/>
    </div>
  </template>
  <a
@@ -48,10 +47,7 @@ function getIconForDiffStatus(pType: DiffStatus) {
    <!-- eslint-disable-next-line vue/no-v-html -->
    <span class="tw-contents" v-html="item.FileIcon"/>
    <span class="gt-ellipsis tw-flex-1">{{ item.DisplayName }}</span>
-    <SvgIcon
-      :name="getIconForDiffStatus(item.DiffStatus).name"
-      :class="getIconForDiffStatus(item.DiffStatus).classes"
-    />
+    <SvgIcon v-bind="diffStatusIcons[item.DiffStatus] ?? diffStatusIcons['']"/>
  </a>
 </template>

--- a/web_src/js/features/repo-diff-filetree.ts
+++ b/web_src/js/features/repo-diff-filetree.ts
@@ -1,10 +1,11 @@
 import {createApp} from 'vue';
 import DiffFileTree from '../components/DiffFileTree.vue';
+import type {DiffFileTreeLocale} from '../modules/diff-file.ts';

 export function initDiffFileTree() {
  const el = document.querySelector('#diff-file-tree');
  if (!el) return;

-  const fileTreeView = createApp(DiffFileTree);
-  fileTreeView.mount(el);
+  const locale = JSON.parse(el.getAttribute('data-locale')!) as DiffFileTreeLocale;
+  createApp(DiffFileTree, {locale}).mount(el);
 }
--- a/web_src/js/features/repo-diff.ts
+++ b/web_src/js/features/repo-diff.ts
@@ -12,6 +12,7 @@ import {invertFileFolding} from './file-fold.ts';
 import {parseDom} from '../utils.ts';
 import {registerGlobalEventFunc, registerGlobalInitFunc} from '../modules/observer.ts';
 import {performFetchActionTrigger} from '../modules/fetch-action.ts';
+import {applyFiltersToFileBoxes, diffTreeStore} from '../modules/diff-file.ts';
 import {initImageDiff} from './imagediff.ts';

 function initDiffFileViewToggle(el: HTMLElement) {
@@ -158,12 +159,11 @@ async function diffLoadMoreFiles(btn: Element): Promise<boolean> {
    const resp = await GET(url);
    if (!resp.ok) return false;
    const respText = await resp.text();
-    const respDoc = parseDom(respText, 'text/html');
+    const respDoc = parseDom(respText, 'text/html'); // the response is a full HTML page, extract the new file boxes from it
    const respFileBoxes = respDoc.querySelector('#diff-file-boxes')!;
-    // the response is a full HTML page, we need to extract the relevant contents:
-    // * append the newly loaded file list items to the existing list
    const respFileBoxesChildren = Array.from(respFileBoxes.children); // "children:HTMLCollection" will be empty after replaceWith
    document.querySelector('#diff-incomplete')!.replaceWith(...respFileBoxesChildren);
+    applyFiltersToFileBoxes(diffTreeStore());
    onDiffFileBodyChange();
    return true;
  } catch (error) {
--- a/web_src/js/modules/diff-file.test.ts
+++ b/web_src/js/modules/diff-file.test.ts
@@ -1,51 +1,140 @@
-import {diffTreeStoreSetViewed, reactiveDiffTreeStore} from './diff-file.ts';
+import {countMatchingFiles, diffTreeStoreSetViewed, extensionFilterFromUrl, extensionFilterToUrl, filterDiffTree, getDiffTreeExtensionStats, reactiveDiffTreeStore, type DiffTreeEntry} from './diff-file.ts';

-test('diff-tree', () => {
-  const store = reactiveDiffTreeStore({
-    'TreeRoot': {
-      'FullName': '',
-      'DisplayName': '',
-      'EntryMode': '',
-      'IsViewed': false,
-      'NameHash': '....',
-      'DiffStatus': '',
-      'FileIcon': '',
-      'Children': [
-        {
-          'FullName': 'dir1',
-          'DisplayName': 'dir1',
-          'EntryMode': 'tree',
-          'IsViewed': false,
-          'NameHash': '....',
-          'DiffStatus': '',
-          'FileIcon': '',
-          'Children': [
-            {
-              'FullName': 'dir1/test.txt',
-              'DisplayName': 'test.txt',
-              'DiffStatus': 'added',
-              'NameHash': '....',
-              'EntryMode': '',
-              'IsViewed': false,
-              'FileIcon': '',
-              'Children': null,
-            },
-          ],
-        },
-        {
-          'FullName': 'other.txt',
-          'DisplayName': 'other.txt',
-          'NameHash': '........',
-          'DiffStatus': 'added',
-          'EntryMode': '',
-          'IsViewed': false,
-          'FileIcon': '',
-          'Children': null,
-        },
-      ],
+function file(name: string, oldName: string = ''): DiffTreeEntry {
+  return {
+    FullName: name,
+    OldFullName: oldName,
+    DisplayName: name.split('/').pop()!,
+    DiffStatus: 'added',
+    NameHash: name,
+    EntryMode: '',
+    IsViewed: false,
+    FileIcon: '',
+    Children: null,
+  };
+}
+
+function dir(name: string, children: DiffTreeEntry[]): DiffTreeEntry {
+  return {
+    FullName: name,
+    OldFullName: '',
+    DisplayName: name.split('/').pop()!,
+    EntryMode: 'tree',
+    IsViewed: false,
+    NameHash: name,
+    DiffStatus: '',
+    FileIcon: '',
+    Children: children,
+  };
+}
+
+function makeStore(children: DiffTreeEntry[]) {
+  return reactiveDiffTreeStore({
+    TreeRoot: {
+      FullName: '', OldFullName: '', DisplayName: '', EntryMode: 'tree', IsViewed: false,
+      NameHash: 'root', DiffStatus: '', FileIcon: '', Children: children,
    },
  }, '', '');
+}
+
+function visibleNames(root: DiffTreeEntry | null): string[] {
+  if (!root) return [];
+  const out: string[] = [];
+  const visit = (e: DiffTreeEntry) => {
+    if (e.EntryMode !== 'tree') out.push(e.FullName);
+    for (const c of e.Children ?? []) visit(c);
+  };
+  visit(root);
+  return out;
+}
+
+test('diff-tree', () => {
+  const store = makeStore([
+    dir('dir1', [file('dir1/test.txt')]),
+    file('other.txt'),
+  ]);
  diffTreeStoreSetViewed(store, 'dir1/test.txt', true);
  expect(store.fullNameMap['dir1/test.txt'].IsViewed).toBe(true);
  expect(store.fullNameMap['dir1'].IsViewed).toBe(true);
 });
+
+test('filterDiffTree', () => {
+  const store = makeStore([
+    dir('dir1', [file('dir1/test.txt')]),
+    file('other.ts'),
+    file('other.TS'),
+  ]);
+
+  store.filenameFilterQuery = 'TesT';
+  expect(visibleNames(filterDiffTree(store))).toEqual(['dir1/test.txt']);
+
+  store.filenameFilterQuery = '';
+  store.activeExtensions = ['.ts'];
+  expect(visibleNames(filterDiffTree(store))).toEqual(['other.ts', 'other.TS']);
+
+  store.activeExtensions = [];
+  expect(visibleNames(filterDiffTree(store))).toEqual([]);
+
+  store.activeExtensions = 'all';
+  expect(visibleNames(filterDiffTree(store))).toEqual(['dir1/test.txt', 'other.ts', 'other.TS']);
+});
+
+test('getDiffTreeExtensionStats', () => {
+  const store = makeStore([
+    dir('dir1', [file('dir1/test.txt'), file('dir1/Makefile'), file('dir1/.gitignore')]),
+    file('.eslintrc.json'), // a dotfile with an extension keeps that extension
+    file('other.ts'),
+    file('other.TXT'), // case-insensitive
+  ]);
+  expect(getDiffTreeExtensionStats(store)).toEqual([
+    {ext: '.json', count: 1},
+    {ext: '.ts', count: 1},
+    {ext: '.txt', count: 2},
+    {ext: 'dotfile', count: 1},
+    {ext: '', count: 1},
+  ]);
+});
+
+test('countMatchingFiles', () => {
+  const store = makeStore([
+    dir('dir1', [file('dir1/new-name.md', 'dir1/old-name.txt')]),
+    file('other.ts'),
+  ]);
+
+  expect(countMatchingFiles(store)).toBe(2);
+
+  // search query also matches the pre-rename path
+  store.filenameFilterQuery = 'old-name';
+  expect(visibleNames(filterDiffTree(store))).toEqual(['dir1/new-name.md']);
+  expect(countMatchingFiles(store)).toBe(1);
+
+  // extension filter only applies to new name
+  store.filenameFilterQuery = '';
+  store.activeExtensions = ['.txt'];
+  expect(visibleNames(filterDiffTree(store))).toEqual([]);
+  expect(countMatchingFiles(store)).toBe(0);
+  store.activeExtensions = ['.md'];
+  expect(visibleNames(filterDiffTree(store))).toEqual(['dir1/new-name.md']);
+
+  store.activeExtensions = ['.md', '.ts'];
+  expect(countMatchingFiles(store)).toBe(2);
+});
+
+test('extensionFilter url round-trip', () => {
+  const known = ['.go', '.ts', 'dotfile', ''];
+  const url = 'http://localhost/owner/repo/pulls/1/files?style=split';
+  const roundTrip = (filter: Parameters<typeof extensionFilterToUrl>[0]) =>
+    extensionFilterFromUrl(new URL(extensionFilterToUrl(filter, url)).search, known);
+
+  expect(extensionFilterToUrl('all', url)).toEqual(url);
+  expect(roundTrip('all')).toEqual('all');
+  expect(roundTrip(['.go', ''])).toEqual(['.go', '']);
+  expect(roundTrip([])).toEqual([]);
+
+  // other query parameters survive, "no extension" gets a stable token
+  expect(extensionFilterToUrl(['.go', ''], url)).toEqual(`${url}&file-filters%5B%5D=.go&file-filters%5B%5D=noextension`);
+
+  // unknown extensions are dropped, selecting every known one is the same as no filter
+  expect(extensionFilterFromUrl('?file-filters[]=.go&file-filters[]=.nope', known)).toEqual(['.go']);
+  expect(extensionFilterFromUrl('?file-filters[]=.go&file-filters[]=.ts&file-filters[]=dotfile&file-filters[]=noextension', known)).toEqual('all');
+});
--- a/web_src/js/modules/diff-file.ts
+++ b/web_src/js/modules/diff-file.ts
@@ -1,12 +1,17 @@
 import {reactive} from 'vue';
 import type {Reactive} from 'vue';
+import {toggleElem} from '../utils/dom.ts';
+import {trString} from './i18n.ts';
+import {basename, extname} from '../utils.ts';

 const {pageData} = window.config;

-export type DiffStatus = '' | 'added' | 'modified' | 'deleted' | 'renamed' | 'copied' | 'typechange';
+// matches statusFromLetter in services/gitdiff/git_diff_tree.go
+export type DiffStatus = '' | 'added' | 'modified' | 'deleted' | 'renamed' | 'copied' | 'typechanged' | 'unmerged' | 'unknown';

 export type DiffTreeEntry = {
  FullName: string,
+  OldFullName: string,
  DisplayName: string,
  NameHash: string,
  DiffStatus: DiffStatus,
@@ -21,6 +26,9 @@ export type DiffFileTreeData = {
  TreeRoot: DiffTreeEntry,
 };

+// activeExtensions: 'all' = no filter (every extension passes); string[] = exact set of extensions allowed (empty = nothing passes).
+type ExtensionFilter = 'all' | string[];
+
 type DiffFileTree = {
  folderIcon: string;
  folderOpenIcon: string;
@@ -28,12 +36,34 @@ type DiffFileTree = {
  fullNameMap: Record<string, DiffTreeEntry>
  fileTreeIsVisible: boolean;
  selectedItem: string;
+  filenameFilterQuery: string;
+  activeExtensions: ExtensionFilter;
+};
+
+type DiffExtensionStats = {
+  ext: string,
+  count: number,
+};
+
+export type DiffExtensionFilterLocale = {
+  filterByFileExtension: string,
+  fileExtensions: string,
+  noFileExtension: string,
+  dotfileExtension: string,
+  allFileExtensions: string,
+};
+
+export type DiffFileTreeLocale = DiffExtensionFilterLocale & {
+  filterFiles: string,
+  filterFilesClear: string,
 };

 let diffTreeStoreReactive: Reactive<DiffFileTree>;
 export function diffTreeStore() {
  if (!diffTreeStoreReactive) {
    diffTreeStoreReactive = reactiveDiffTreeStore(pageData.DiffFileTree!, pageData.FolderIcon!, pageData.FolderOpenIcon!);
+    const knownExtensions = getDiffTreeExtensionStats(diffTreeStoreReactive).map((stat) => stat.ext);
+    diffTreeStoreReactive.activeExtensions = extensionFilterFromUrl(window.location.search, knownExtensions);
  }
  return diffTreeStoreReactive;
 }
@@ -58,25 +88,149 @@ function fillFullNameMap(map: Record<string, DiffTreeEntry>, entry: DiffTreeEntr
 }

 export function reactiveDiffTreeStore(data: DiffFileTreeData, folderIcon: string, folderOpenIcon: string): Reactive<DiffFileTree> {
-  const store = reactive({
+  const store = reactive<DiffFileTree>({
    diffFileTree: data,
    folderIcon,
    folderOpenIcon,
    fileTreeIsVisible: false,
    selectedItem: '',
+    filenameFilterQuery: '',
+    activeExtensions: 'all',
    fullNameMap: {},
  });
  fillFullNameMap(store.fullNameMap, data.TreeRoot);
  return store;
 }

+export const extDotfile = 'dotfile'; // bucket for ".gitignore" and friends, real extensions always start with a dot
+
+const urlParamFileFilters = 'file-filters[]'; // same parameter GitHub uses, lists the selected extensions
+const urlValueNoExtension = 'noextension';
+
+export function extensionFilterFromUrl(search: string, knownExtensions: string[]): ExtensionFilter {
+  const params = new URLSearchParams(search);
+  if (!params.has(urlParamFileFilters)) return 'all';
+  const extensions = params.getAll(urlParamFileFilters)
+    .filter(Boolean)
+    .map((ext) => ext === urlValueNoExtension ? '' : ext)
+    .filter((ext) => knownExtensions.includes(ext));
+  return extensions.length === knownExtensions.length ? 'all' : extensions;
+}
+
+export function extensionFilterToUrl(filter: ExtensionFilter, url: string): string {
+  const parsed = new URL(url);
+  parsed.searchParams.delete(urlParamFileFilters);
+  if (filter !== 'all') {
+    if (!filter.length) parsed.searchParams.append(urlParamFileFilters, '');
+    for (const ext of filter) parsed.searchParams.append(urlParamFileFilters, ext || urlValueNoExtension);
+  }
+  return parsed.href;
+}
+
+function getFileExtension(filename: string): string {
+  const ext = extname(filename).toLowerCase();
+  if (ext) return ext;
+  return basename(filename).startsWith('.') ? extDotfile : '';
+}
+
+function extensionRank(ext: string): number {
+  if (!ext) return 2;
+  return ext === extDotfile ? 1 : 0;
+}
+
+export function getDiffTreeExtensionStats(store: Reactive<DiffFileTree>): DiffExtensionStats[] {
+  const extensionMap = new Map<string, number>();
+  for (const entry of Object.values(store.fullNameMap)) {
+    if (entry.EntryMode === 'tree' || !entry.FullName) continue;
+    const ext = getFileExtension(entry.FullName);
+    extensionMap.set(ext, (extensionMap.get(ext) ?? 0) + 1);
+  }
+  return Array.from(extensionMap, ([ext, count]) => ({ext, count}))
+    .sort((a, b) => extensionRank(a.ext) - extensionRank(b.ext) || a.ext.localeCompare(b.ext));
+}
+
+function buildFilter(store: Reactive<DiffFileTree>) {
+  const query = store.filenameFilterQuery.trim().toLowerCase();
+  const exts = store.activeExtensions === 'all' ? null : new Set(store.activeExtensions);
+  if (!query && !exts) return null;
+  return (newName: string, oldName: string) => {
+    if (query && !newName.toLowerCase().includes(query) && !oldName.toLowerCase().includes(query)) return false;
+    return !exts || exts.has(getFileExtension(newName));
+  };
+}
+
+// Children===null marks a file leaf; everything else (incl. the root, which has EntryMode="") is recursed into.
+export function filterDiffTree(store: Reactive<DiffFileTree>): DiffTreeEntry | null {
+  const matches = buildFilter(store);
+  if (!matches) return store.diffFileTree.TreeRoot;
+  const visit = (entry: DiffTreeEntry): DiffTreeEntry | null => {
+    if (entry.Children === null) return matches(entry.FullName, entry.OldFullName) ? entry : null;
+    const children = entry.Children.map(visit).filter((child): child is DiffTreeEntry => child !== null);
+    if (!children.length) return null;
+    return {...entry, Children: children};
+  };
+  return visit(store.diffFileTree.TreeRoot);
+}
+
+export function countMatchingFiles(store: Reactive<DiffFileTree>): number {
+  const matches = buildFilter(store);
+  let totalMatchingFilesCount = 0;
+  for (const entry of Object.values(store.fullNameMap)) {
+    if (entry.EntryMode === 'tree' || !entry.FullName) continue;
+    if (!matches || matches(entry.FullName, entry.OldFullName)) totalMatchingFilesCount++;
+  }
+  return totalMatchingFilesCount;
+}
+
+function countEveryFileInDiff(store: Reactive<DiffFileTree>): number {
+  let totalFilesCount = 0;
+  for (const entry of Object.values(store.fullNameMap)) {
+    if (entry.EntryMode !== 'tree' && entry.FullName) totalFilesCount++;
+  }
+  return totalFilesCount;
+}
+
+function updateLoadProgress(loadedFiles: number, totalFiles: number) {
+  const el = document.querySelector('#diff-load-progress');
+  if (!el) return;
+  el.textContent = trString(el.getAttribute('data-text-too-many-files')!, loadedFiles, totalFiles);
+}
+
+function updateShowMoreButton(matchingBelow: number) {
+  const btn = document.querySelector('#diff-show-more-files');
+  if (!btn) return;
+  if (matchingBelow > 0) {
+    btn.textContent = trString(btn.getAttribute('data-text-matching')!, matchingBelow);
+  } else {
+    btn.textContent = btn.getAttribute('data-text-default')!;
+  }
+}
+
+export function applyFiltersToFileBoxes(store: Reactive<DiffFileTree>) {
+  const boxes = document.querySelectorAll<HTMLElement>('#diff-file-boxes .diff-file-box[data-new-filename]');
+  const matches = buildFilter(store);
+  if (!matches) {
+    for (const box of boxes) toggleElem(box, true);
+    toggleElem('#diff-no-matches', false);
+    updateShowMoreButton(0);
+    updateLoadProgress(boxes.length, countEveryFileInDiff(store));
+    return;
+  }
+  let visibleCount = 0;
+  for (const box of boxes) {
+    const matched = matches(box.getAttribute('data-new-filename')!, box.getAttribute('data-old-filename')!);
+    if (matched) visibleCount++;
+    toggleElem(box, matched);
+  }
+  const matchingCount = countMatchingFiles(store);
+  updateShowMoreButton(matchingCount - visibleCount);
+  updateLoadProgress(boxes.length, countEveryFileInDiff(store));
+  toggleElem('#diff-no-matches', matchingCount === 0);
+}
+
 function isEntryViewed(entry: DiffTreeEntry): boolean {
  if (entry.Children) {
-    let count = 0;
-    for (const child of entry.Children) {
-      if (child.IsViewed) count++;
-    }
-    return count === entry.Children.length;
+    return entry.Children.every((child) => child.IsViewed);
  }
  return entry.IsViewed;
 }
--- a/web_src/js/modules/tippy.test.ts
+++ b/web_src/js/modules/tippy.test.ts
@@ -0,0 +1,16 @@
+import {availableSizeForPlacement} from './tippy.ts';
+
+test('availableSizeForPlacement', () => {
+  const rect = (values: Partial<DOMRect>) => values as DOMRect;
+  vi.spyOn(window, 'innerHeight', 'get').mockReturnValue(1000);
+  vi.spyOn(window, 'innerWidth', 'get').mockReturnValue(800);
+
+  // on the placement axis it is the gap to the edge the popup opens towards, the viewport on the other
+  expect(availableSizeForPlacement(rect({top: 400, bottom: 432}), 'bottom-end', 0)).toEqual({width: 784, height: 560});
+  expect(availableSizeForPlacement(rect({top: 400, bottom: 432}), 'top-end', 0)).toEqual({width: 784, height: 392});
+  expect(availableSizeForPlacement(rect({left: 100, right: 300}), 'right', 0)).toEqual({width: 492, height: 984});
+  expect(availableSizeForPlacement(rect({left: 100, right: 300}), 'left', 0)).toEqual({width: 92, height: 984});
+
+  // the placement offset eats into the space on that axis
+  expect(availableSizeForPlacement(rect({top: 400, bottom: 432}), 'bottom-end', -6).height).toEqual(554);
+});
--- a/web_src/js/modules/tippy.ts
+++ b/web_src/js/modules/tippy.ts
@@ -7,8 +7,11 @@ import {stripTags} from '../utils.ts';
 type TippyOpts = {
  role?: string,
  theme?: 'default' | 'tooltip' | 'menu' | 'box-with-header' | 'bare',
+  limitSizeToViewport?: {horizontal?: boolean, vertical?: boolean}, // cap to the viewport and scroll the content
 } & Partial<Props>;

+type PopperModifier = NonNullable<NonNullable<Props['popperOptions']>['modifiers']>[number];
+
 const visibleInstances = new Set<Instance>();
 const arrowSvg = html`<svg width="16" height="7"><path d="m0 7 8-7 8 7Z" class="tippy-svg-arrow-outer"/><path d="m0 8 8-7 8 7Z" class="tippy-svg-arrow-inner"/></svg>`;

@@ -20,10 +23,46 @@ function arrowPadding({placement, reference}: {placement: Placement, reference:
  return Math.max(0, Math.min(3, referenceLength / 2 - 8)); // 8 = half of arrow width
 }

+const viewportPadding = 8;
+
+// space left on the side the popup opens towards, the viewport on the other axis
+export function availableSizeForPlacement(referenceRect: DOMRect, placement: string, offset: number): {width: number, height: number} {
+  const gap = Math.abs(offset) + viewportPadding;
+  const spanWidth = window.innerWidth - viewportPadding * 2;
+  const spanHeight = window.innerHeight - viewportPadding * 2;
+  const side = placement.split('-')[0];
+  if (side === 'top') return {width: spanWidth, height: referenceRect.top - gap};
+  if (side === 'bottom') return {width: spanWidth, height: window.innerHeight - referenceRect.bottom - gap};
+  if (side === 'left') return {width: referenceRect.left - gap, height: spanHeight};
+  return {width: window.innerWidth - referenceRect.right - gap, height: spanHeight};
+}
+
+// popper does not constrain size, publish it for the styles. Replaced by floating-ui's "size" on migration
+function sizeModifier(limit: {horizontal?: boolean, vertical?: boolean}): PopperModifier {
+  return {
+    name: 'tippyLimitSize',
+    enabled: true,
+    phase: 'beforeWrite',
+    requires: ['computeStyles'], // runs after "flip" and "offset", so both are final
+    fn({state}) {
+      const offset = state.modifiersData.offset?.[state.placement];
+      const isVertical = state.placement.startsWith('top') || state.placement.startsWith('bottom');
+      const available = availableSizeForPlacement(
+        state.elements.reference.getBoundingClientRect(),
+        state.placement,
+        (isVertical ? offset?.y : offset?.x) ?? 0,
+      );
+      const {style} = state.elements.popper;
+      if (limit.horizontal) style.setProperty('--tippy-max-width', `${Math.max(0, Math.floor(available.width))}px`);
+      if (limit.vertical) style.setProperty('--tippy-max-height', `${Math.max(0, Math.floor(available.height))}px`);
+    },
+  };
+}
+
 export function createTippy(target: Element, opts: TippyOpts = {}): Instance {
  // the callback functions should be destructured from opts,
  // because we should use our own wrapper functions to handle them, do not let the user override them
-  const {onHide, onShow, onDestroy, role, theme, arrow, ...other} = opts;
+  const {onHide, onShow, onDestroy, role, theme, arrow, limitSizeToViewport, ...other} = opts;
  // CSS theme, either "default", "tooltip", "menu", "box-with-header" or "bare"
  const resolvedTheme = theme || role || 'default';
  const resolvedArrow = arrow ?? (resolvedTheme === 'bare' ? false : arrowSvg);
@@ -56,7 +95,10 @@ export function createTippy(target: Element, opts: TippyOpts = {}): Instance {
      return onShow?.(instance);
    },
    arrow: resolvedArrow,
-    popperOptions: {modifiers: [{name: 'arrow', options: {padding: arrowPadding}}]},
+    popperOptions: {modifiers: [
+      {name: 'arrow', options: {padding: arrowPadding}},
+      ...limitSizeToViewport ? [sizeModifier(limitSizeToViewport)] : [],
+    ]},
    // HTML role attribute, ideally the default role would be "popover" but it does not exist
    role: role || 'menu',
    theme: resolvedTheme,
@@ -68,6 +110,7 @@ export function createTippy(target: Element, opts: TippyOpts = {}): Instance {
  if (instance.props.role === 'menu') {
    target.setAttribute('aria-haspopup', 'true');
  }
+  if (limitSizeToViewport) instance.popper.setAttribute('data-tippy-limit-size', '');

  return instance;
 }
--- a/web_src/js/svg.ts
+++ b/web_src/js/svg.ts
@@ -22,6 +22,7 @@ import octiconClock from '../../public/assets/img/svg/octicon-clock.svg';
 import octiconCode from '../../public/assets/img/svg/octicon-code.svg';
 import octiconColumns from '../../public/assets/img/svg/octicon-columns.svg';
 import octiconCopy from '../../public/assets/img/svg/octicon-copy.svg';
+import octiconDash from '../../public/assets/img/svg/octicon-dash.svg';
 import octiconDiffAdded from '../../public/assets/img/svg/octicon-diff-added.svg';
 import octiconDiffModified from '../../public/assets/img/svg/octicon-diff-modified.svg';
 import octiconDiffRemoved from '../../public/assets/img/svg/octicon-diff-removed.svg';
@@ -112,6 +113,7 @@ const svgs = {
  'octicon-code': octiconCode,
  'octicon-columns': octiconColumns,
  'octicon-copy': octiconCopy,
+  'octicon-dash': octiconDash,
  'octicon-diff-added': octiconDiffAdded,
  'octicon-diff-modified': octiconDiffModified,
  'octicon-diff-removed': octiconDiffRemoved,
--- a/web_src/js/utils.test.ts
+++ b/web_src/js/utils.test.ts
@@ -17,6 +17,9 @@ test('basename', () => {
 });

 test('extname', () => {
+  expect(extname('.gitignore')).toEqual('');
+  expect(extname('/path/to/.gitignore')).toEqual('');
+  expect(extname('/path/to/.eslintrc.json')).toEqual('.json');
  expect(extname('/path/to/file.js')).toEqual('.js');
  expect(extname('/path/')).toEqual('');
  expect(extname('/path')).toEqual('');
--- a/web_src/js/utils.ts
+++ b/web_src/js/utils.ts
@@ -13,12 +13,11 @@ export function basename(path: string): string {
  return lastSlashIndex < 0 ? path : path.substring(lastSlashIndex + 1);
 }

-/** transform /path/to/file.ext to .ext */
+/** transform /path/to/file.ext to .ext, dotfiles like /path/to/.gitignore have no extension */
 export function extname(path: string): string {
-  const lastSlashIndex = path.lastIndexOf('/');
  const lastPointIndex = path.lastIndexOf('.');
-  if (lastSlashIndex > lastPointIndex) return '';
-  return lastPointIndex < 0 ? '' : path.substring(lastPointIndex);
+  if (lastPointIndex <= path.lastIndexOf('/') + 1) return '';
+  return path.substring(lastPointIndex);
 }

 /** test whether a variable is an object */