Render content-identical renames using the previous file path (#8907)

* Initial plan

* Fix base path for renamed files

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Apply remaining changes

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Attestation commit

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/@types/vscode.proposed.chatParticipantAdditions.d.ts

@@ -573,19 +573,14 @@ declare module 'vscode' {
 	}
 
 	/**
-	 * Represents an auto-mode model routing resolution. Displayed as a collapsible
-	 * widget in the chat stream showing which model was selected and why.
+	 * Explains what the "Auto" model routed a turn to, as a single status line.
+	 * Push a part without a model for the in-flight state, then a resolved one.
+	 * Auto may route several times in a turn; each route gets its own row.
 	 */
 	export class ChatResponseAutoModeResolutionPart {
-		/** The model ID that was selected by the router */
-		resolvedModel: string;
-		/** The user-facing display name of the resolved model */
-		resolvedModelName: string;
-		/** The router's classification label */
-		predictedLabel: string;
-		/** Confidence score (0-1) from the router */
-		confidence: number;
-		constructor(resolvedModel: string, resolvedModelName: string, predictedLabel: string, confidence: number);
+		/** The model the router picked, or `undefined` while routing is in flight. */
+		resolvedModel: { id: string; name: string } | undefined;
+		constructor(resolvedModel?: { id: string; name: string });
 	}
 
 	export interface ChatResponseStream {

src/test/view/fileChangeModel.test.ts

@@ -0,0 +1,57 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { default as assert } from 'assert';
+import { createSandbox, SinonSandbox } from 'sinon';
+import * as vscode from 'vscode';
+import { GitChangeType, InMemFileChange } from '../../common/file';
+import { FolderRepositoryManager } from '../../github/folderRepositoryManager';
+import { PullRequestModel } from '../../github/pullRequestModel';
+import { GitFileChangeModel } from '../../view/fileChangeModel';
+import { MockRepository } from '../mocks/mockRepository';
+
+describe('GitFileChangeModel', function () {
+	let sinon: SinonSandbox;
+
+	beforeEach(function () {
+		sinon = createSandbox();
+	});
+
+	afterEach(function () {
+		sinon.restore();
+	});
+
+	it('loads base content from the previous filename for a rename', async function () {
+		const repository = new MockRepository();
+		const baseCommit = 'base';
+		const fileName = 'src/b/thing.py';
+		const previousFileName = 'src/a/thing.py';
+		const baseContent = 'print("unchanged")';
+		const show = sinon.stub(repository, 'show').resolves(baseContent);
+		const change = new InMemFileChange(
+			baseCommit,
+			GitChangeType.RENAME,
+			fileName,
+			previousFileName,
+			'',
+			[],
+			'https://example.com/thing.py',
+		);
+		const model = new GitFileChangeModel(
+			{ repository } as unknown as FolderRepositoryManager,
+			{} as PullRequestModel,
+			change,
+			vscode.Uri.joinPath(repository.rootUri, fileName),
+			vscode.Uri.joinPath(repository.rootUri, previousFileName),
+			'head',
+		);
+
+		assert.strictEqual(await model.showBase(), baseContent);
+		assert.strictEqual(show.calledOnceWithExactly(
+			baseCommit,
+			vscode.Uri.joinPath(repository.rootUri, previousFileName).fsPath,
+		), true);
+	});
+});

src/view/fileChangeModel.ts

@@ -120,7 +120,11 @@ export class GitFileChangeModel extends FileChangeModel {
 	async showBase(): Promise<string | undefined> {
 		if (!this._show && this.change.status !== GitChangeType.ADD) {
 			const commit = ((this.change instanceof InMemFileChange || this.change instanceof SlimFileChange) ? this.change.baseCommit : this.sha!);
-			const absolutePath = vscode.Uri.joinPath(this.folderRepoManager.repository.rootUri, this.fileName).fsPath;
+			const fileName = (this.change.status === GitChangeType.RENAME) &&
+				(this.change instanceof InMemFileChange || this.change instanceof SlimFileChange)
+				? this.change.previousFileName!
+				: this.fileName;
+			const absolutePath = vscode.Uri.joinPath(this.folderRepoManager.repository.rootUri, fileName).fsPath;
 			this._show = this.folderRepoManager.repository.show(commit, absolutePath);
 		}
 		return this._show;