convert an Arch ALPM package to a debian package

alpm-2-deb.sh

#!/usr/bin/env bash

set -euo pipefail

ORIG=$(pwd)
TEMP=$(mktemp -d)

cleanup() {
  local status=$?
  cd "$ORIG" || true
  rm -rf "$TEMP" || true
  exit "$status"
}

trap cleanup EXIT INT TERM ERR

if [ $# -ne 1 ]; then
  echo "usage: $0 <alpm package>" >&2
  exit 1
fi

ALPM=$(realpath -- "$1")

if [ ! -f "$ALPM" ]; then
  echo "$ALPM does not exist" >&2
  exit 2
fi

tar -xf "$ALPM" -C "$TEMP"
cd "$TEMP"
NAME=$(sed -n 's/^pkgname = //p' .PKGINFO)

mkdir "$NAME"
find "$TEMP" -mindepth 1 -maxdepth 1 ! -name "$NAME" -exec mv -t "$TEMP/$NAME" -- {} +
cd "$NAME"

mkdir -p DEBIAN

NAME=$(sed -n 's/^pkgname = //p' .PKGINFO)
PKGVER=$(sed -n 's/^pkgver = //p'  .PKGINFO)
PKGDESC=$(sed -n 's/^pkgdesc = //p' .PKGINFO)
ARCH_RAW=$(sed -n 's/^arch = //p'  .PKGINFO)
MAINT=$(sed -n 's/^packager = //p' .PKGINFO)

case "$ARCH_RAW" in
  x86_64)  ARCH=amd64 ;;
  aarch64) ARCH=arm64 ;;
  *)       ARCH="$ARCH_RAW" ;;   # fall-back: keep original if unknown
esac

docdir="usr/share/doc/$NAME"
mkdir -p "$docdir"
# store the original metadata files in /usr/share/doc/$NAME
# if they are missing after installation, it's because of /etc/dpkg/dpkg.cfg.d/excludes
for src in .BUILDINFO .MTREE .PKGINFO .INSTALL; do
  [ -f "$src" ] || continue

  dst=${src#.} # strip off the .
  mv -- "$src" "$docdir/$dst"
done

echo -e "$NAME ($PKGVER) unstable; urgency=low\n\n  * ALPM→DEB auto-convert\n\n -- $MAINT  $(date -R)" \
     | gzip -n9 > "usr/share/doc/$NAME/changelog.Debian.gz"

echo "building $NAME"

cat > DEBIAN/control <<EOF
Package: $NAME
Version: $PKGVER
Description: $PKGDESC
Architecture: $ARCH
Maintainer: $MAINT
Section: misc
Priority: optional
EOF

cd ..
DEBFILE="${NAME}_${PKGVER}_${ARCH}.deb"
fakeroot dpkg-deb --build "$NAME" "$TEMP/$DEBFILE" >&2 > /dev/null
mv "$TEMP/$DEBFILE" "$ORIG"
cd "$ORIG"
echo "created $DEBFILE"