Small bash script that determines by which packages a Brew package is used.

witch.sh

#!/bin/bash
if [[ -z "$1" ]]; then

    echo "usage: witch [package name]"

else

    # iterate over all installed packages
    for pkg in $( brew list ); do

        # iterate over all their dependencies
        for dep in $( brew deps $pkg ); do
            if [ "$dep" == "$1" ]; then
                echo "$pkg"
            fi
        done
    done

fi