title: `source $MYVIMRC` doesn't work when i delete some content, but it does work when i add some content
body: <p><code>:source $MYVIMRC</code> doesn't work when I delete some content in .vimrc, but it will work when I add some content.</p>
  
  <p>I want to enable a setting which is typing <code>@@</code> then it will automatically show my email, so I add a line in my .vimrc file like this <code>iabbrev @@ XXX@gmail.com</code> and <code>:w</code> to save the file. After that, I turn to my source file, then I type <code>:source $MYVIMRC</code>, It works as expected. BUT, If I remove the line <code>iabbrev @@ xxx@gmail.com</code> and save .vimrc file.  Again, I turn to my source file, then I type <code>:source $MYVIMRC</code>, It still works. Only I quit the file and reopen it. The changes can effect. How can I make the DELETE changes effect without quitting the file? </p>
  
  <p>Comment out the line is the same as removing the line. <code>:source $MYVIMRC</code> doesn't effect. It effects only I quit the file and reopen it the newer .vimrc will work.</p>
  
  <p>I am not a native speaker, please ask me if you don't understand my problem. </p>
  
  <p>Thank you very much! </p>