From "How core Git developers configure Git" https://news.ycombinator.com/item?id=43179071 :

skwp/git-workflows-book > .gitconfig appendix: https://github.com/skwp/git-workflows-book : > "Two useful aliases: unstage and uncommit": https://github.com/skwp/git-workflows-book#two-useful-aliase... :

  [alias]
  unstage = reset HEAD              # remove files from index (tracking)
  uncommit = reset --soft HEAD^     # go back before last commit, with files in uncommitted state