Add contributing guidelines.

Author: matthias_schaub

README.md

@@ -15,17 +15,48 @@ Please refer to the documentation for more information: https://mapswipe-workers
 
 ## Ressources
 
-- GitHub repository of the MapSwipe Back-End: https://github.com/mapswipe/python-mapswipe-workers
-- GitHub repository of the MapSwipe Website: https://github.com/mapswipe/mapswipe.github.io
-- GitHub repository of the MapSwipe App https://github.com/mapswipe/mapswipe
-- Website of MapSwipe: https://mapswipe.org
-- OSM-Wiki page of MapSwipe: https://wiki.openstreetmap.org/wiki/MapSwipe
+- MapSwipe Back-End: https://github.com/mapswipe/python-mapswipe-workers
+- MapSwipe App https://github.com/mapswipe/mapswipe
+- MapSwipe Website: https://mapswipe.org
+- MapSwipe OSM-Wiki: https://wiki.openstreetmap.org/wiki/MapSwipe
+
+
+## Contributing Guidelines
+
+### Feature Branch
+
+To contribute to the MapSwipe back-end please create dedicated feature branches based on the `dev` branch. After the changes create a Pull Request of the `feature` branch into the `dev` branch on GitHub:
+
+```bash
+git checkout dev
+git checkout -b featureA
+# Hack away ...
+git commit -am 'Describe changes.'
+git push -u origin featureA
+# Create a Pull Request from feature branch into the dev branch on GitHub.
+```
+
+> Note: If a bug in production (master branch) needs fixing before a new versions of MapSwipe Workers gets released (merging dev into master branch), a hotfix branch should be created. In the hotfix branch the bug should be fixed and then merged with the master branch (and also dev).
+
+
+### Style Guide
+
+This project uses [black](https://github.com/psf/black) and [flake8](https://gitlab.com/pycqa/flake8) to achieve a unified style.
+
+Use [pre-commit](https://pre-commit.com/) to run `black` and `flake8` prior to any git commit. `pre-commit`, `black` and `flake8` should already be installed in your virtual environment since they are listed in `requirements.txt`. To setup pre-commit simply run:
+
+```
+pre-commit install
+```
+
+From now on `black` and `flake8` should run automatically whenever `git commit` is executed.
 
 
 ## License
 
 This project is licensed under the Apache License 2.0 - see the [LICENSE](LICENSE) file for details
 
+
 ## Authors
 
 * **Benjamin Herfort** - HeiGIT - [Hagellach37](https://github.com/Hagellach37)
@@ -34,6 +65,7 @@ This project is licensed under the Apache License 2.0 - see the [LICENSE](LICENS
 
 See also the list of [contributors](contributors.md) who participated in this project.
 
+
 ## Acknowledgements
 
 * Humanitarian organizations can't help people if they can't find them.