title: Accidentally merged other branches when using `git pull` with no arguments
body: <p>Not knowing any better, I'd always used blissfully <code>git pull</code> (without arguments) to get remote updates.</p>
  
  <p>Now that we're using branches, this has come back to haunt me.</p>
  
  <p>After doing a <code>git pull</code>, I noticed that my local master had been merged with the other branches as well, whereas on the remote, the branches are not merged.  </p>
  
  <p>I'm trying to figure out how this happened so that I can avoid doing it again in the future, but no luck so far.</p>
  
  <p>I didn't put anything strange in my .git/config file.</p>