Answers for "bootstrap 4 link used in css file example"

revert local commit

$ git reset --hard HEAD~1

undo most recent commit

$ git commit -m "some comment"                
$ git reset HEAD~                                          
<< edit files as necessary >>                              
$ git add ...                                              
$ git commit -c ORIG_HEAD

bootstrap cdn

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">