git-tbranch.sh

#!/bin/bash
# based on http://stackoverflow.com/a/18647857/652904
declare PROGNAME="${0}"


function Usage()
{
  local -i EXITCODE=${1}; shift

  echo "${@}" >&2

cat<<_EOF_ >&2
  ${@}
  Usage:
    ${PROGNAME} <branchname> [git-branch-options]

  git-branch-options are passed into git-branch after the branch name

_EOF_

  exit ${EXITCODE}
}



BRNAME=$1; shift
[ -z "${BRNAME}" ] && Usage 1 "Missing branchname"

# exit on fail
set -e

git branch "${BRNAME}" "${@}"
git checkout "${BRNAME}"
git config branch."${BRNAME}".remote origin
git config branch."${BRNAME}".merge refs/heads/"${BRNAME}"
git config branch."${BRNAME}".rebase true

Kudos to Gregory McIntyre, for his underappriciated answer on http://stackoverflow.com/a/18647857/652904. It did exactly what I needed, I just made it into a full, slightly safer script that also allows specification of <start-point>.