Sometimes right after you perform a commit in git you realize you made a mistake. For me it is usually that I commit a file I didn't want to or wasn't ready to.

The good news is that as long as you haven't pushed it to a remote repository it is relatively easy to fix.

Just perform the following steps:

$ git reset HEAD~

# Make the necessary changes

$ git add .
$ git commit -c ORIG_HEAD

That is it. You have now fixed your mistake.