Retrieve automatically changes when sys/fetch_changesets is called

# How to configure redmine to automatically fetch changes?

You have to do the following settings in github.com and in the redmine app.
**For github.com:**
- go to github.com repo settings. And put the Redmine API key generated as Redmine service hook.
Put valid project id.
- Check all options in github
** Fetch Commits
** Update Redmine Issues About Commits
** Active

**For redmine:**
- go to Administration > Settings > Repositories, Generate key and add it to github.com
- Add valid ssh key with no password to the passenger user which runs redmine. Usually this is apache or www-data. (Use PassengerDefaultUser setting in the apache config to set the rails user in passenger).
- Add the ssh key to the profile in github which will retrieve the changes