Add modal dialog for handling uncommitted changes during PR checkout (#7111)

* Initial plan

* Implement modal dialog for uncommitted changes in pr.pick command

- Add handleUncommittedChanges helper function with modal dialog
- Integrate uncommitted changes check before PR checkout
- Support Stage changes, Discard changes, and Cancel options
- Follow existing patterns from copilotRemoteAgent.ts

Co-authored-by: osortega <48293249+osortega@users.noreply.github.com>

* Add tests and documentation for modal dialog implementation

- Create unit tests for uncommitted changes detection
- Add comprehensive manual testing guide
- Verify implementation follows existing patterns

Co-authored-by: osortega <48293249+osortega@users.noreply.github.com>

* Stash

* Address reviewer feedback: update stash API usage and remove ineffective tests

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

* Fix stash API method names and remove empty test file

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

* I led Copilot astray. There is no `stash` method 🤦‍♀️

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: osortega <48293249+osortega@users.noreply.github.com>
Co-authored-by: Osvaldo Ortega <osortega@microsoft.com>
Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: 3 people

src/commands.ts

@@ -47,6 +47,62 @@ import {
 import { PRNode } from './view/treeNodes/pullRequestNode';
 import { RepositoryChangesNode } from './view/treeNodes/repositoryChangesNode';
 
+// Modal dialog options for handling uncommitted changes during PR checkout
+const STASH_CHANGES = vscode.l10n.t('Stash changes');
+const DISCARD_CHANGES = vscode.l10n.t('Discard changes');
+
+/**
+ * Shows a modal dialog when there are uncommitted changes during PR checkout
+ * @param repository The git repository with uncommitted changes
+ * @returns Promise<boolean> true if user chose to proceed (after staging/discarding), false if cancelled
+ */
+async function handleUncommittedChanges(repository: Repository): Promise<boolean> {
+	const hasWorkingTreeChanges = repository.state.workingTreeChanges.length > 0;
+	const hasIndexChanges = repository.state.indexChanges.length > 0;
+
+	if (!hasWorkingTreeChanges && !hasIndexChanges) {
+		return true; // No uncommitted changes, proceed
+	}
+
+	const modalResult = await vscode.window.showInformationMessage(
+		vscode.l10n.t('You have uncommitted changes that would be overwritten by checking out this pull request.'),
+		{
+			modal: true,
+			detail: vscode.l10n.t('Choose how to handle your uncommitted changes before checking out the pull request.'),
+		},
+		STASH_CHANGES,
+		DISCARD_CHANGES,
+	);
+
+	if (!modalResult) {
+		return false; // User cancelled
+	}
+
+	try {
+		if (modalResult === STASH_CHANGES) {
+			// Stash all changes (working tree changes + any unstaged changes)
+			const allChangedFiles = [
+				...repository.state.workingTreeChanges.map(change => change.uri.fsPath),
+				...repository.state.indexChanges.map(change => change.uri.fsPath),
+			];
+			if (allChangedFiles.length > 0) {
+				await repository.add(allChangedFiles);
+				await vscode.commands.executeCommand('git.stash', repository);
+			}
+		} else if (modalResult === DISCARD_CHANGES) {
+			// Discard all working tree changes
+			const workingTreeFiles = repository.state.workingTreeChanges.map(change => change.uri.fsPath);
+			if (workingTreeFiles.length > 0) {
+				await repository.clean(workingTreeFiles);
+			}
+		}
+		return true; // Successfully handled changes, proceed with checkout
+	} catch (error) {
+		vscode.window.showErrorMessage(vscode.l10n.t('Failed to handle uncommitted changes: {0}', formatError(error)));
+		return false;
+	}
+}
+
 function ensurePR(folderRepoManager: FolderRepositoryManager, pr?: PRNode): PullRequestModel;
 function ensurePR<TIssue extends Issue, TIssueModel extends IssueModel<TIssue>>(folderRepoManager: FolderRepositoryManager, pr?: TIssueModel): TIssueModel;
 function ensurePR<TIssue extends Issue, TIssueModel extends IssueModel<TIssue>>(folderRepoManager: FolderRepositoryManager, pr?: PRNode | TIssueModel): TIssueModel {
@@ -530,6 +586,21 @@ export function registerCommands(
 				pullRequestModel = pr;
 			}
 
+			// Get the folder manager to access the repository
+			const folderManager = reposManager.getManagerForIssueModel(pullRequestModel);
+			if (!folderManager) {
+				return vscode.window.showErrorMessage(vscode.l10n.t('Unable to find repository for this pull request.'));
+			}
+
+			// If we don't have a repository from the node, use the one from the folder manager
+			const repositoryToCheck = repository || folderManager.repository;
+
+			// Check for uncommitted changes before proceeding with checkout
+			const shouldProceed = await handleUncommittedChanges(repositoryToCheck);
+			if (!shouldProceed) {
+				return; // User cancelled or there was an error handling changes
+			}
+
 			const fromDescriptionPage = pr instanceof PullRequestModel;
 			/* __GDPR__
 			"pr.checkout" : {