Many open-source communities have guidelines to their contributors concerning coding style and developer workflow. For example some like to have commit messages to there code base to adhere to certain rules.

Write a client side git hook to enforce the first sentence of the commit message begins in a capital letter and ends with a full stop (period) and contains only 50 characters or less. You can use a scripting language of your choice (eg: python, ruby, bash).

Useful Links -

http://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks