Describe the problem you are trying to solve

During development you are very often in the process of making changes and then build or run your project or run your tests. This always costs some time, therefore an automation would be useful, to save some time and increase the developer experience

Describe the solution you'd like

I'd like to have a built-in watcher similar to nodemon for NodeJS or like this project https://github.com/passcod/cargo-watch
This would allow you to run your whole project if you change something or you can also specify to run only tests when your files change:
cargo watch -x run
cargo watch -x test

Since this is completely optional to use, developers are not forced to use the suggested watcher.

Notes