`dx serve` potentially messed up Cargo.toml during rebase - do not rebuild during rebase?

## Feature Request

When running `dx serve` on my codebase, it happens from time to time that it tries to rebuild my app _while_ I am doing a `git rebase --autosquash` (for example).

## Implement Suggestion

My idea here would be to make `dx serve` aware of the git repository and automatically _not_ rebuilding when it notices that a rebase is ongoing.