Policies for pull requests. Coding style.

README.md

@@ -53,9 +53,49 @@ sudo ./venv/bin/letsencrypt
 
 ## Hacking
 
-1. Bootstrap: `./venv/bin/python setup.py dev`
+In order to start hacking, you will first have to create a development
+environment:
 
-2. Test code base: `./venv/bin/tox`
+`./venv/bin/python setup.py dev`
+
+The code base, including your pull requests, **must have 100% test
+statement coverage and be compliant with the [coding
+style](#coding-style)**. The following tools are there to help you:
+
+- `./venv/bin/tox` starts a full set of tests. Please make sure you
+  run it before submitting a new pull request.
+
+- `./venv/bin/tox -e cover` checks the test coverage only.
+
+- `./venv/bin/tox -e lint` checks the style of the whole project,
+  while `./venv/bin/pylint file` will check a single `file` only.
+
+### Coding style
+
+Most importantly, *be consistent with the rest of the code*, please.
+
+1. Read [PEP 8 - Style Guide for PythonCode]
+(https://www.python.org/dev/peps/pep-0008).
+
+2. Follow [Google Python Style Guide]
+(https://google-styleguide.googlecode.com/svn/trunk/pyguide.html),
+with the following exception that we use
+[Sphinx](http://sphinx-doc.org/)-style documentation:
+
+   ```python
+   def foo(arg):
+       """Short description.
+
+       :param int arg: Some number.
+
+       :returns: Argument
+       :rtype: int
+
+       """
+       return arg
+   ```
+
+3. Remember to use `./venv/bin/pylint`.
 
 ## Command line usage