This is a great idea, thanks for it! I've done similar things with using fzf to git add, git diff, and so on, but I hadn't thought of using it to pick a commit to rebase from.

I made a few changes so I figured I'd post them back here in case you're interested:

    pick-commit = # equivalent to your git log... cut...
    rif = "!f() { rev=$(git pick-commit); [[ $rev ]] && git ri $rev~; }; f"

"rif" = "rebase interactive fzf/fuzzyfind". The function and test just makes it exit cleanly if you escape out of the filter instead of giving "fatal: invalid upstream '~'" (and I changed it from ^ to ~ because I think ~ is usually what one should use over ^, but I'm willing to be corrected). And obviously I already have 'ri' aliased to 'rebase -i'.

While I'm here, here are my similar git aliases for adding, diffing, etc. files using fzf:

    pick-status-files = "!f() { git status -z | xargs -0n1 | cut -c4- | fzi --print0 | xargs -0to git "$@"; }; f"
    af = !git pick-status-files add
    # and so on for diff, difftool, checkout, etc.

Oh, and 'fzi' (fuzzy-inline) is a small shell script that just calls:

    fzf --height 30% --reverse --multi "$@"