Completion for git commands
A solution when switching from ubuntu is to use homebrew, a package manager for Mac OSX. In particular, for git, you will have included a number of additions including bash completion. This will be true for other programs which are faliliar for developpers, like make.

In 2 steps: 


install with ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"
Run brew doctor to get your path set up properly
Install git and bash completion: brew install git bash-completion
Add the command return in the previous step in your .bash_profile.
Restart your bash sessions once the new tools and configuration are written to your file system. 


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