title: Changing the Git username
body: <p>I use Git GNU bash, version 4.3.42(5)-release (x86_64-pc-msys)
   windows 8.1 pro.
  I gave it a username at the very beginning by typing the command:
      git config --global user.name"xyz"
  but then when i've got to Github, this username was already taken, so i tried to change my Git username to be the same as the one Github. Typing the same command
  then typing :
      git config --list 
  but it keeps showing the old username, i've tried even to uninstall it, and then retype the same command, but it's the same issue.
  Someone maybe can tell me how to fix it ?</p>