git scripting: How to list all git branches containing a commit

I can list all branches containing a certain commit using git branch --list --contains just fine. But as explained in the related question on how to list all branches, this is a porcelain command that should not be used in scripts.

The latter question suggests to use the plumbing command git for-each-ref, but that does not support --contains.

What is the correct plumbing interface to list all branches that contain a certain commit.

One possible solution using the plumbing commands git-for-each-ref and git merge-base (the latter suggested by Joachim himself):

#!/bin/sh

# git-branchesthatcontain.sh
#
# List the local branches that contain a specific revision
#
# Usage: git branchthatcontain <rev>
#
# To make a Git alias called 'branchesthatcontain' out of this script,
# put the latter on your search path, and run
#
#   git config --global alias.branchesthatcontain \
#       '!sh git-branchesthatcontain.sh'

if [ $# -ne 1 ]; then
    printf "%s\n\n" "usage: git branchesthatcontain <rev>"
    exit 1
fi

rev=$1

git for-each-ref --format='%(refname:short)' refs/heads | \
    while read ref; do
        if git merge-base --is-ancestor "$rev" "$ref"; then
            printf "%s\n" "$ref"
        fi;
    done

exit $?

The script is available at jub0bs/git-aliases on GitHub.

(Edit: thanks to coredump for showing me how to get rid of that nasty eval.)