Have you upgraded to OS X El Capitan from App Store ?
Have you suddenly started getting the following error in your project?
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
If yes, then here is the solution
xcode-select --install
Remember, in MAC git is attached to XCode’s Command line tools.