title: Git - change file
body: <p>I've made new repository and made couple commits. I haven't pushed it anywhere so nobody cares  whether history changes.<br>
  I made mistake in first commit (the whole file is wrong) and I need it to change in all further commits (from the first, so all).
  How can it be done?
  If I already have some tags, will I have to re-tag them?</p>