In a script called `git-first-push`, on your path:

    #!/bin/zsh

    git push -u ${1:-origin} HEAD:"$(git symbolic-ref -q HEAD | sed -e 's|^refs/heads/||')"

This means "push the current branch to origin (or the first argument, if specified) to a branch of the same name, when this hasn't been done before. Set origin (or the first arg) as the upstream of the local branch". Formally invoked as `git first-push [remote]`, I just alias it to `git fp`.

EDIT: I've forgotten offhand whether there are actual zsh-isms here. It's probably bash compatible, but I always have zsh installed by the time this script lands on a system.