Try
rm -f ./.git/index.lock
In your repository directory. The error message is rather explicit as to what causes it typically, so if you have no other git processes running (which is the normal case), go ahead and delete that file.
Try
rm -f ./.git/index.lock
In your repository directory. The error message is rather explicit as to what causes it typically, so if you have no other git processes running (which is the normal case), go ahead and delete that file.