I have recently upgraded from Yosemite to El Capitan. I had GIT setup and tab auto-complete was absolutely working fine. However, when I upgraded to El Capitan, I opened a terminal window and whenever I tried to auto complete GIT commands it was showing the following error:
xcrun error active developer path
Only the following command should resolve the issue if you are the admin on the machine.
xcode-select --install
Cheers!