Crashes if `metamask-module-template` already exists in temp directory but is not a Git repo

Start in src/cli.ts at the template-fetching logic around the failing git pull call. Reproduce the case with an existing metamask-module-template directory that lacks .git, then verify that the tool handles that directory appropriately and no longer remains stuck with the fetching spinner.

I've tried using both npx @metamask/template-sync and yarn dlx @metamask/template-sync on a project and get the same error:

⠋ Fetching module template.Error: Command failed with exit code 128: git pull
fatal: not a git repository (or any of the parent directories): .git
    at makeError (/private/var/folders/gz/d8jvtc0n0rncp1xz80k0x62m0000gn/T/xfs-cd883ffe/dlx-65796/node_modules/execa/lib/error.js:60:11)
    at handlePromise (/private/var/folders/gz/d8jvtc0n0rncp1xz80k0x62m0000gn/T/xfs-cd883ffe/dlx-65796/node_modules/execa/index.js:118:26)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async task (/private/var/folders/gz/d8jvtc0n0rncp1xz80k0x62m0000gn/T/xfs-cd883ffe/dlx-65796/node_modules/@metamask/template-sync/dist/cli.js:36:21)
    at async main (/private/var/folders/gz/d8jvtc0n0rncp1xz80k0x62m0000gn/T/xfs-cd883ffe/dlx-65796/node_modules/@metamask/template-sync/dist/cli.js:114:9) {
  shortMessage: 'Command failed with exit code 128: git pull',
  command: 'git pull',
  escapedCommand: 'git pull',
  exitCode: 128,
  signal: undefined,
  signalDescription: undefined,
  stdout: '',
  stderr: 'fatal: not a git repository (or any of the parent directories): .git',
  failed: true,
  timedOut: false,
  isCanceled: false,
  killed: false
}
⠼ Fetching module template.

It looks like this line is failing. This happens if a metamask-module-template directory already exists in the temporary directory root but is not a Git repository for some reason.

(Also, for some reason, the tool doesn't exit, but the spinner next to "Fetching module template" keeps spinning, but that seems like a separate issue.)

It seems like we ought to check that a .git directory exists in the metamask-module-template directory instead.