#!/usr/bin/env bash

doit() {
        local filename=$1
	{
		<"$filename" sed -r \
		 -e "s|(/\.\.)*/config.mk|/$(realpath -ms --relative-to="$(dirname -- "$filename")" config.mk)|" \
		 -e '/^nested\.subdirs/d' \
		 -e '/^include \$\(topsrcdir\)\/build-aux\/Makefile\.tail\.mk$/d'
		echo
		find "$(dirname "$filename")" -mindepth 2 -maxdepth 2 -name Makefile -print0 |
		    xargs -r0 dirname -z -- |
		    xargs -r0 basename -a -z |
		    xargs -r0 printf 'nested.subdirs += %s\n' | sort
		echo
		echo 'include $(topsrcdir)/build-aux/Makefile.tail.mk'
	} | cat -s | build-aux/write-ifchanged "$filename"
}

main() {
	set -e
	set -o pipefail
        local filename
        for filename in "$@"; do
		>&2 printf ' => %q %q\n' "$0" "$filename"
                doit "$filename"
        done
}

main "$@"