As a fan of atomic commits, I sometimes find myself with some changes that are ready to stage that belong on an earlier commit. If it is the immediately previous, I'll do an --amend. For anything further back than that, I've come to love the use of git commit --fixup <SHA>.

Once one or more fixup commits are on the current branch, they'll need to be squashed into the commits for which they've been targeted. This calls for a git rebase.

Git knows how to squash fixup commits into the correct place, but you have to tell it to do so automatically. You can do that one of two ways.

You can either include the --autosquash flag each time you rebase:

$ git rebase -i --autosquash

Or you can tell Git to always autosquash in your ~/.gitconfig:

[rebase]
	autoSquash = true

See the section on --autosquash in man git-rebase for more details.