📝 Update the Contributing documentation

* Remove the outdated `flit` section
* Mention pre-commit and how to use it
* Describe how to set-up the development dependencies
* Describe how to run tests

docs/contributing.md

@@ -4,7 +4,82 @@ First, you might want to see the basic ways to [help Typer and get help](help-ty
 
 If you already cloned the repository and you know that you need to deep dive in the code, here are some guidelines to set up your environment.
 
-### Virtual environment with `venv`
+### Pre-commit hooks
+
+We use <a href="https://pre-commit.com/" class="external-link" target="_blank">pre-commit</a> to run checks and formatting before submitting code for review.
+
+#### Install pre-commit
+
+We recommend <a href="https://pipx.pypa.io/" class="external-link" target="_blank">pipx</a> to install pre-commit in an isolated environment.
+
+=== "pipx"
+
+    <div class="termy">
+
+    ```console
+    $ pipx install pre-commit
+    ```
+
+    </div>
+
+=== "pip"
+
+    <div class="termy">
+
+    ```console
+    $ pip install pre-commit
+    ```
+
+    </div>
+
+=== "Homebrew"
+
+    <div class="termy">
+
+    ```console
+    $ brew install pre-commit
+    ```
+
+    </div>
+
+=== "Conda"
+
+    <div class="termy">
+
+    ```console
+    $ conda install pre-commit
+    ```
+
+    </div>
+
+#### Activate hooks on the repository
+
+By activating the hooks we instruct git to run the checks before every commit.
+
+<div class="termy">
+
+```console
+$ pre-commit install
+```
+
+</div>
+
+!!! note
+    It's only needed once. From that point on, every time you commit, the pre-commit hooks will run, checking and formating the files you are committing.
+
+#### Run checks manually
+
+You can also manually run the checks on all files with:
+
+<div class="termy">
+
+```console
+$ pre-commit run --all-files
+```
+
+</div>
+
+### Virtual environment
 
 You can create a virtual environment in a directory using Python's `venv` module:
 
@@ -18,7 +93,7 @@ $ python -m venv env
 
 That will create a directory `./env/` with the Python binaries and then you will be able to install packages for that isolated environment.
 
-### Activate the environment
+#### Activate the environment
 
 Activate the new environment with:
 
@@ -87,54 +162,18 @@ If it shows the `pip` binary at `env/bin/pip` then it worked. 🎉
 
     This makes sure that if you use a terminal program installed by that package (like `flit`), you use the one from your local environment and not any other that could be installed globally.
 
-### Flit
+### Install Typer
 
-**Typer** uses <a href="https://flit.readthedocs.io/en/latest/index.html" class="external-link" target="_blank">Flit</a> to build, package and publish the project.
-
-After activating the environment as described above, install `flit`:
+With the virtual environment activated, you can install Typer in "editable" mode:
 
 <div class="termy">
 
 ```console
-$ pip install flit
-
----> 100%
+$ pip install --editable .
 ```
 
 </div>
 
-Now re-activate the environment to make sure you are using the `flit` you just installed (and not a global one).
-
-And now use `flit` to install the development dependencies:
-
-=== "Linux, macOS"
-
-    <div class="termy">
-
-    ```console
-    $ flit install --deps develop --symlink
-
-    ---> 100%
-    ```
-
-    </div>
-
-=== "Windows"
-
-    If you are on Windows, use `--pth-file` instead of `--symlink`:
-
-    <div class="termy">
-
-    ```console
-    $ flit install --deps develop --pth-file
-
-    ---> 100%
-    ```
-
-    </div>
-
-It will install all the dependencies and your local Typer in your local environment.
-
 #### Using your local Typer
 
 If you create a Python file that imports and uses Typer, and run it with the Python from your local environment, it will use your local Typer source code.
@@ -143,36 +182,6 @@ And if you update that local Typer source code, as it is installed with `--symli
 
 That way, you don't have to "install" your local version to be able to test every change.
 
-### Format
-
-There is a script that you can run that will format and clean all your code:
-
-<div class="termy">
-
-```console
-$ bash scripts/format.sh
-```
-
-</div>
-
-It will also auto-sort all your imports.
-
-For it to sort them correctly, you need to have Typer installed locally in your environment, with the command in the section above using `--symlink` (or `--pth-file` on Windows).
-
-### Format imports
-
-There is another script that formats all the imports and makes sure you don't have unused imports:
-
-<div class="termy">
-
-```console
-$ bash scripts/format-imports.sh
-```
-
-</div>
-
-As it runs one command after the other and modifies and reverts many files, it takes a bit longer to run, so it might be easier to use `scripts/format.sh` frequently and `scripts/format-imports.sh` only before committing.
-
 ## Docs
 
 The documentation uses <a href="https://www.mkdocs.org/" class="external-link" target="_blank">MkDocs</a>.
@@ -218,6 +227,32 @@ That way, you can edit the documentation/source files and see the changes live.
 
 ## Tests
 
+Typer uses <a href="https://docs.pytest.org/" class="external-link" target="_blank">pytest</a> for testing.
+
+Make sure you have the development dependencies installed:
+
+<div class="termy">
+
+```console
+$ pip install -e requirements-tests.txt
+```
+
+</div>
+
+### Running tests
+
+To run the tests, you can use the `pytest` command:
+
+<div class="termy">
+
+```console
+$ pytest -v
+```
+
+</div>
+
+### Coverage report
+
 There is a script that you can run locally to test all the code and generate coverage reports in HTML:
 
 <div class="termy">