Contributing guide

Please read the following before you create an issue or send a pull request.

General advice

Do not commit on the master branch. Always create a feature branch which branches off the latest commit (HEAD) on master. Pull requests are being merged to the master branch.
```
      C---D---E feature
     /         \
A---B-----------F master
```
Keep your master branch clean. This will allow to pull upstream changes without conflicts or the need to merge.
Put changes into atomic (context-wise) commits. Clean up your branch before you open a pull request. Feel free to rebase your work on your branch and force push it. Never rebase work which has been pushed to master.
Pull master before you open a pull request. If master changed in the meantime, rebase your branch onto the latest commit on master. This will ensure that your changes do not conflict with other changes which have been made on master. It is your job to sort out any conflicts before your branch is merged.

Add a GeoJSON file for your city containing the market data and a metadata block.
Please apply automatic formatting for the GeoJSON file using the editor of your choice.
You might wanna use German spelling with Umlauts for city names which is supported.
Add your city to the list of supported cities in the README.md.

Always try to answer the question "Why?" in your commit message.
State a brief summary in the first line, feel free to explain details under a blank line in the description part. See Git Commit Messages.
Check for lint errors.
Create and run tests.