I'm working in a repository made by someone else, and it includes a build file.

This build file should NOT change upstream, however in order for it to build on my system I needed to make some OS-specific changes to the file.

Is there a way to tell git "hey, don't commit this file, and just leave it the way it is" without either removing my modifications to the file or sending my modifications upstream?

@rachel the problem is I keep having to revert my branches because I accidentally type "git commit -a"

(because I'm used to a mercurial workflow)