Linked Answers Q: https://answers.atlassian.com/questions/112557/git-amend-a-commit-do-more-than-change-the-message?page=1

Basically need to be able to do a commit and specify you want to amend the previous commit but also unstage/stage files from the previous commit if you like (as well as hunks). This is done using --soft of the reset command, this way it can be reverted if cancelled.