Git has a number of awesome features; Not least of all is the ability to amend the previous commit. If you ever find that you accidentally left something out of your last commit, be it a file or an extra change to a file that you just committed, don't worry. It can easily be fixed
All you have to do is stage the extra changes like you would for a normal commit:
git add .
And then just commit with the
git commit --amend
If you don't specify a commit message with
-m you will be prompted with the previous commit message as a default.
When you're done you can check
git log --stat to see your amended commit with the extra changes. For more information, check out Git's 'commit' documentation.
Hope that was helpful.