how to fix git always asking username and password.

   1. using SSH instead of https

　　　　　　git remote set-url origin git@github.com:username/repo.git

2.storing the username and password 
　　　　　git config --global credential.helper store
   or save them for just one session 
　　　　　git config --global credential.helper cache
　　or set a timer for them
        git config -- global credential.helper 'cache --timeout=600'