Add issue management within git

Hi,

This would be awesome to handle issue directly with git: Having an offline version of the issues synced to the gitlab/github issues. A lot of work is done on the issues and it is lost when migrating from one service to the other. Beside we don’t always have a good internet connection. There is already a kind of integration between commit message fixing issue automatically when merged in the master branch (with “fix #143’).

Kind regards,

Martin