git-rewrite

#!/bin/bash

rebase_opts=()

base=
debug=0
find_base=0
use_upstream=0
use_master=0
use_origin_master=0

setup_force() {
    export GIT_SEQUENCE_EDITOR='printf "\r"; sed "/^\$/q"'
}

while :; do
    case $1 in
        -d|--debug)
            debug=1 ;;
        -m|--master)
            use_master=1 ;;
        -o|--origin-master)
            use_origin_master=1 ;;
        -f|--force)
            setup_force ;;
        -?*)
            rebase_opts+=("$1") ;;
        *)
            break
    esac
    shift
done

if (( use_master )); then
    base=master
    method=argument
elif (( use_origin_master )); then
    base=origin/master
    method=argument
elif [[ $1 ]]; then
    base=$1
    method=argument
elif base=$(git rev-parse --quiet --verify "@{u}" 2>/dev/null); then
    method=upstream
elif branch=$(git symbolic-ref --short HEAD) &&
     firstcommit=$(git rev-list --topo-order --reverse $branch --not --exclude=$branch --branches | head -n 1); then
    base="$firstcommit~"
    method=discovery
fi

if (( debug )); then
    printf 'Using base %s by %s\n' "$base" "$method"
fi

git rebase --update-refs --autostash "${rebase_opts[@]}" --keep-base -i "$base"