Git uri handler clone should preserve branch

[joyceerhl]

1. Invoke vscode-insiders://git.clone?https://github.com/microsoft/vscode/tree/release/1.70
2. Select a directory to clone your repo into
3. Open cloned repo
4. 🐛 branch context is not preserved

This impacts Continue Working On--branch context is preserved for Clone in Container and Create New Codespace.

I propose adding a new optional query parameter to the uri handler here:

vscode/extensions/git/src/protocolHandler.ts

Lines 26 to 33 in 6cc5256

	private clone(uri: Uri): void {
	const data = querystring.parse(uri.query);
	if (!data.url) {
	console.warn('Failed to open URI:', uri);
	return;
	}

and passing that to the git.clone command as an optional argument here

vscode/extensions/git/src/protocolHandler.ts

Line 59 in 6cc5256

commands.executeCommand('git.clone', cloneUri.toString(true));

Then after cloning here:

vscode/extensions/git/src/commands.ts

Lines 517 to 521 in 6cc5256

	const repositoryPath = await window.withProgress(
	opts,
	(progress, token) => this.git.clone(url!, { parentPath: parentPath!, progress, recursive: options.recursive }, token)
	);

and before opening the repo in a new window, we would perform the ref checkout:

if (ref) {
    const repository = this.model.getRepository(Uri.file(repositoryPath));
    await repository?.checkout(ref);
}

[lszomoru]

@joyceerhl, will you create a test plan item/verification steps for this feature?

[joyceerhl]

@lszomoru yes I will!