If you happen to use many open sourced libraries hosted on Github's repositories for your iOS apps, then you should take a look at GitHub for Mac.
On the GitHub web site, you can watch many different repositories in order to keep an eye of what is happening with them. But, what if you use only a few of those repos and want to keep a local copy on your Mac for inclusion into your development workflow? I use GitHub for Mac for this purpose.
Double-click on any repos to see the most recent activities on it. Hit the Changes section on the left and see what has changed between your local copy and the master on GitHub. Hit Branches to have a look at the repository's different branches then merge if you like.
GitHub for Mac allows the complete management of repositories hosted on GitHub. As I'm not an expert, I found GitHub for Mac useful nonetheless.
Download it here.