An excerpt from my ~/.gitconfig, showing a related approach (piggy-backing on git-revise):

  [alias]
   # Revise into the commit that last changed File
   rf = "!f() { if [ $# -eq 0 ]; then REV=\"$(git status --porcelain --untracked-files=no | sed '/^ /d;s/^.. //' | xargs -n1 git rev-list -1 HEAD --)\"; NUM_REVS=\"$(echo \"$REV\" | wc -l)\"; if [ $NUM_REVS -ne 1 ]; then >&2 echo Files in the index were not all last modified in the same commit; exit 1; fi; else REV=\"$(git rev-list -1 HEAD -- \"$1\")\"; shift; fi; git revise \"$REV\" \"$@\"; }; f"

(This alias is three times as long as my next longest aliases, which are ports of Mercurial’s id, tip, incoming and outgoing commands.)

This is more coarse-grained than the technique in this article, as it only goes down to the file level—because that was sufficient for me when I wrote the alias, and probably easier to implement. I’ve been vaguely contemplating trying git-autofixup and git-absorb for a while too, which include what are essentially more polished and powerful versions of my alias.