git-relative-path

#!/bin/sh
set -e

root="$(git root)"
realpath_bin="$(which grealpath realpath 2>/dev/null | head -n1 || true)"

if [ ! -x "$realpath_bin" ]; then
    echo "'realpath' or 'grealpath' utility not found. Please install GNU coreutils." >&2
    exit 1
fi

if ! "$realpath_bin" --version 2>/dev/null | grep -q GNU; then
    echo "I expected the 'realpath' utility to be the GNU version." >&2
    echo "$realpath_bin: not the GNU version" >&2
    echo "Please install GNU coreutils and try again." >&2
    exit 2
fi

while [ $# -gt 0 ]; do
    "$realpath_bin" --relative-to=. "$root/$1"
    shift
done