Function createAndSwitch

packages/computer/src/git/cli.ts:1334–1352

* Create a branch (optionally at a start point) and move HEAD to * it — the shared core of `checkout -b` and `switch -c`. The * branch is created first; only on success does HEAD move, so a * name collision leaves the working tree untouched.

(
  client: GitClient,
  dir: string,
  name: string,
  startPoint: string | undefined,
  subcommand: string,
)

 * name collision leaves the working tree untouched.
 */
async function createAndSwitch(
  client: GitClient,
  dir: string,
  name: string,
  startPoint: string | undefined,
  subcommand: string,
): Promise<GitCliResult> {
  try {
    await client.branch({ dir, name, startPoint, force: false });
  } catch (cause) {
    return mapGitError(subcommand, cause);
  }
  try {
    await client.checkout({ dir, ref: name });
    return { stdout: "", stderr: "", exitCode: 0 };
  } catch (cause) {
    return mapGitError(subcommand, cause);
  }
}

// ---------------------------------------------------------------
// fetch