Suggest `feature.manyFiles` when appropriate

### Is your feature request related to a problem? Please describe.
Some Git operations, including `status` can get slow on repos with big files, or too many files

### Describe the solution you'd like
Suggest `git config feature.manyFiles true` in such scenarios

### Describe alternatives you've considered
The config could be set automatically.

As a last resort, the user could try a `sparse-checkout`

### Additional context