title: untracked working tree files in git
body: <p>Every once in a while while I'm developing, I start to accumulate "untracked working tree files" and all I'm doing is <code>git pull</code> most of the time. Still, every once in a while I can't do a pull because of the aforementioned "untracked working tree files". Sometimes I do a <code>git clean</code> just so I can pull or checkout. What are untracked working tree files? Why am I accumulating them when I'm just doing pulls? Most importantly, why are untracked files preventing me from doing anything? (git warns me that they will be overwritten, but I don't care most of the time. I'm not sure when I would care, so I don';t quite get why git is set to prevent me from doing things when they might be overwritten...)</p>