title: Change all versions of a file without commiting
body: <p>I have a bunch of C header files that use a generic <code>#ifndef XXXXXX</code> naming structure. I'd like to modify all of those header file to <code>#ifndef YYYYYYY</code>, and save the changes in the git repo without having to commit. Is it possible to change a file (or multiple files) and ripple those changes in all previous commits? Or is it possible to change a bunch of files and save the changes in the repo without commiting at all?</p>