git version 1.8.3.msysgit.0
From https://github.com/dolphin-emu/dolphin
   2d6810b..32e0544  master     -> origin/master
fatal: Unable to create 'c:/Users/buildbot/Slaves/dolphin/wip-win-x64/build/.git/index.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.