genenter

#!/bin/sh
set -eu

CWD="$(dirname "$0")"
ROOT="${ROOT:-$PWD/broot}"
REPOS="$PWD/repos"
DISTDIR="$PWD/distfiles"
PKGDIR="$PWD/packages"

mkdir -p "$REPOS.wrk"
mkdir -p "$DISTDIR" "$PKGDIR"

tmp="$(mktemp -d -t geniso.XXXXXXXXXX)"
mount -o lowerdir="$REPOS",upperdir="$ROOT",workdir="$REPOS.wrk" -t overlay overlay "$tmp"

mount -t tmpfs tmpfs "$tmp/mnt"
mkdir "$tmp/mnt/build" "$tmp/mnt/scripts" "$tmp/mnt/distfiles"
mount --bind "$PWD" "$tmp/mnt/build"
mount --bind -o ro "$CWD" "$tmp/mnt/scripts"
mount --bind -o ro "$(portageq envvar DISTDIR)" "$tmp/mnt/distfiles"

mkdir -p "$tmp/usr/portage/distfiles"
mkdir -p "$tmp/usr/portage/packages"
mount --bind "$DISTDIR" "$tmp/usr/portage/distfiles"
mount --bind "$PKGDIR" "$tmp/usr/portage/packages"

mount -o nosuid,noexec,nodev -t sysfs sysfs "$tmp/sys"
mount -o nosuid,noexec,nodev -t proc proc "$tmp/proc"
mount -o nosuid,noexec -t devtmpfs devtmpfs "$tmp/dev"
mount -o nosuid,noexec -t devpts devpts "$tmp/dev/pts"

trap true INT
env -i TERM=linux HOME=/root chroot "$tmp" /bin/bash -l "$@" || true

umount "$tmp/dev/pts" "$tmp/dev" "$tmp/proc" "$tmp/sys"
umount "$tmp/usr/portage/packages" "$tmp/usr/portage/distfiles"
umount "$tmp/mnt/build" "$tmp/mnt/scripts" "$tmp/mnt/distfiles" "$tmp/mnt"
umount "$tmp"
rm -r "$tmp"