By using git commit amend you can add files if you forgot to do that to your most recent commit. I’ve written about undoing a commit before, and also about undoing pushed commits. which you also could use in this scenario. But this is a bit faster.
Say you’ve made changes in asdf.txt, and added a new file called fdsa.txt with very important stuff in it. You are very happy with the results and commit it.
git commit -a -m 'Doing changes'
Exactly after hitting enter you realized you forgot to run git add – . to begin to track and stage fdsa.txt This is where amend comes in. But first run add.
git add -- .
to add this file to the commit you just recently made all you got to do is run this command:
git commit --amend
Git commit official docs
This trick amends the new commit to the latest one made. Read more about the git commit command at the official Git site.