git-remerge

#!/bin/sh

merge() {
  git merge --no-edit --no-verify origin/$1
  git mergetool || exit 1
  git commit --no-edit --no-verify
}

#git fetch
read commit p1 p2 <<<$(git rev-list --parents HEAD -n1)
[ -z "$p2" ] && exit 0
upstream=$(upstream.rb $p1)
merged=$(upstream.rb $p2)
merge $merged
merge $upstream
new_commit=$(git show -s --format=%B $commit | perl -0pe 's/\n*\Z/\n/' | git commit-tree -p origin/$upstream -p origin/$merged $(git write-tree))
git reset $new_commit