Uh huh, now imagine you've built something with usage in mind, rather than a hodgepodge of leaky abstractions for what's happening behind the scenes:
git undo
git undo file
git undo
git undo file
And to add to the fun, there's multiple other answers in this thread on how to accomplish the same task.
git reset --soft HEAD^
# make changes so index only contains what you want
git commit -a -C ORIG_HEAD
git config --global alias.undo reset --soft HEAD^
git config --global alias.redo commit -a -C ORIG_HEAD
git undo
# make changes so index only contains what you want
git redo
ORIG_HEAD is set to point to the most recent HEAD when using reset. See "man git-reset" > EXAMPLES > "Undo a commit and redo".