Add URI handler for opening multidiff editor (#8310)

* Initial plan

* Add URL handling for opening multidiff editor for a PR

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

* Refactor: Extract common PR resolution logic into helper method

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

---------

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/common/uri.ts

@@ -668,7 +668,8 @@ function validateOpenWebviewParams(owner?: string, repo?: string, number?: strin
 export enum UriHandlerPaths {
 	OpenIssueWebview = '/open-issue-webview',
 	OpenPullRequestWebview = '/open-pull-request-webview',
-	CheckoutPullRequest = '/checkout-pull-request'
+	CheckoutPullRequest = '/checkout-pull-request',
+	OpenPullRequestChanges = '/open-pull-request-changes'
 }
 
 export interface OpenIssueWebviewUriParams {
@@ -709,11 +710,16 @@ export async function toOpenPullRequestWebviewUri(params: OpenPullRequestWebview
 	return vscode.env.asExternalUri(vscode.Uri.from({ scheme: vscode.env.uriScheme, authority: EXTENSION_ID, path: UriHandlerPaths.OpenPullRequestWebview, query }));
 }
 
+export async function toOpenPullRequestChangesUri(params: OpenPullRequestWebviewUriParams): Promise<vscode.Uri> {
+	const query = JSON.stringify(params);
+	return vscode.env.asExternalUri(vscode.Uri.from({ scheme: vscode.env.uriScheme, authority: EXTENSION_ID, path: UriHandlerPaths.OpenPullRequestChanges, query }));
+}
+
 export function fromOpenOrCheckoutPullRequestWebviewUri(uri: vscode.Uri): OpenPullRequestWebviewUriParams | undefined {
 	if (compareIgnoreCase(uri.authority, EXTENSION_ID) !== 0) {
 		return;
 	}
-	if (uri.path !== UriHandlerPaths.OpenPullRequestWebview && uri.path !== UriHandlerPaths.CheckoutPullRequest) {
+	if (uri.path !== UriHandlerPaths.OpenPullRequestWebview && uri.path !== UriHandlerPaths.CheckoutPullRequest && uri.path !== UriHandlerPaths.OpenPullRequestChanges) {
 		return;
 	}
 	try {

src/test/common/uri.test.ts

@@ -109,5 +109,23 @@ describe('uri', () => {
 			const result2 = fromOpenOrCheckoutPullRequestWebviewUri(uri2);
 			assert.strictEqual(result2, undefined);
 		});
+
+		it('should work for open-pull-request-changes path', () => {
+			const uri = vscode.Uri.parse('vscode://github.vscode-pull-request-github/open-pull-request-changes?uri=https://github.com/test/example/pull/999');
+			const result = fromOpenOrCheckoutPullRequestWebviewUri(uri);
+
+			assert.strictEqual(result?.owner, 'test');
+			assert.strictEqual(result?.repo, 'example');
+			assert.strictEqual(result?.pullRequestNumber, 999);
+		});
+
+		it('should parse JSON format for open-pull-request-changes path', () => {
+			const uri = vscode.Uri.parse('vscode://github.vscode-pull-request-github/open-pull-request-changes?%7B%22owner%22%3A%22testowner%22%2C%22repo%22%3A%22testrepo%22%2C%22pullRequestNumber%22%3A123%7D');
+			const result = fromOpenOrCheckoutPullRequestWebviewUri(uri);
+
+			assert.strictEqual(result?.owner, 'testowner');
+			assert.strictEqual(result?.repo, 'testrepo');
+			assert.strictEqual(result?.pullRequestNumber, 123);
+		});
 	});
 });

src/uriHandler.ts

@@ -118,6 +118,8 @@ export class UriHandler implements vscode.UriHandler {
 				// Simplified format example: vscode-insiders://github.vscode-pull-request-github/checkout-pull-request?uri=https://github.com/microsoft/vscode-css-languageservice/pull/460
 				// Legacy format example: vscode-insiders://github.vscode-pull-request-github/checkout-pull-request?%7B%22owner%22%3A%22alexr00%22%2C%22repo%22%3A%22playground%22%2C%22pullRequestNumber%22%3A714%7D
 				return this._checkoutPullRequest(uri);
+			case UriHandlerPaths.OpenPullRequestChanges:
+				return this._openPullRequestChanges(uri);
 		}
 	}
 
@@ -134,7 +136,7 @@ export class UriHandler implements vscode.UriHandler {
 		return IssueOverviewPanel.createOrShow(this._telemetry, this._context.extensionUri, folderManager, issue);
 	}
 
-	private async _openPullRequestWebview(uri: vscode.Uri): Promise<void> {
+	private async _resolvePullRequestFromUri(uri: vscode.Uri): Promise<{ folderManager: FolderRepositoryManager; pullRequest: PullRequestModel } | undefined> {
 		const params = fromOpenOrCheckoutPullRequestWebviewUri(uri);
 		if (!params) {
 			return;
@@ -144,7 +146,23 @@ export class UriHandler implements vscode.UriHandler {
 		if (!pullRequest) {
 			return;
 		}
-		return PullRequestOverviewPanel.createOrShow(this._telemetry, this._context.extensionUri, folderManager, pullRequest);
+		return { folderManager, pullRequest };
+	}
+
+	private async _openPullRequestWebview(uri: vscode.Uri): Promise<void> {
+		const resolved = await this._resolvePullRequestFromUri(uri);
+		if (!resolved) {
+			return;
+		}
+		return PullRequestOverviewPanel.createOrShow(this._telemetry, this._context.extensionUri, resolved.folderManager, resolved.pullRequest);
+	}
+
+	private async _openPullRequestChanges(uri: vscode.Uri): Promise<void> {
+		const resolved = await this._resolvePullRequestFromUri(uri);
+		if (!resolved) {
+			return;
+		}
+		return PullRequestModel.openChanges(resolved.folderManager, resolved.pullRequest);
 	}
 
 	private async _savePendingCheckoutAndOpenFolder(params: { owner: string; repo: string; pullRequestNumber: number }, folderUri: vscode.Uri): Promise<void> {