At any stage, you may want to undo something. Here, we’ll review a few basic tools for undoing changes that you’ve made. Be careful, because you can’t always revert some of these undos. This is one of the few areas in Git where you may lose some work if you do it wrong.
Changing Your Last Commit
One of the common undos takes place when you commit too early and possibly forget to add some files, or you mess up your commit message. If you want to try that commit again, you can run commit with the --amend option:
$ git commit --amend
This command takes your staging area and uses it for the commit. If you’ve made no changes since your last commit (for instance, you run this command immediately after your previous commit), then your snapshot will look exactly the same and all you’ll change is your commit message.
The same commit-message editor fires up, but it already contains the message of your previous commit. You can edit the message the same as always, but it overwrites your previous commit."