Just for archlinux and still needs heavy testing

downgrade_pkgver.sh

#!/bin/bash

#Author: Swift Geek swiftgeek@gmɐil.com

#TODO: Check for pacman
#TODO: Check for db.lock
#TODO: Lock db.lock
#TODO: Check if package is as old as told in arg
#TODO: Log this info to pacman log
#TODO: Check if there is anything passed as argument`
#TODO: Target_pkgver from arg

target_pkgver=0-0
pkgname="$1"

[ -z "$@" ] && echo "No args passed!" && exit 1

/usr/bin/pacman -Qsq "$pkgname" > /dev/null
if [ "$?" = "0" ]; then
  orig_pkgver=$(/usr/bin/pacman -Qs "^$pkgname\$" | grep 'local/' | awk '{print $2}')
  [ "$orig_pkgver" = "$target_pkgver" ] && echo 'Already downgraded!' && exit 0
  pkgdir="/var/lib/pacman/local/${pkgname}" # WARNING: doesn't contain version

  #RW stage
  if [ -n "$orig_pkgver" -a -d "${pkgdir}-${orig_pkgver}" ]; then
    echo "Exist && nonzero. Proceed to sedding"
    sed -i '/\%VERSION\%/{n; s/.*/'"$target_pkgver"'/}' "${pkgdir}-${orig_pkgver}/desc"
    [ "$?" != 0 ] && echo "Failed at sedding desc file" && exit 1 # TODO fix this when stdout is innaccesible :< terrbile bug
    echo "Proceed to moving"
    mv "${pkgdir}-${orig_pkgver}" "${pkgdir}-${target_pkgver}"
    [ "$?" != 0 ] && echo "Failed at renaming pkgdir" && exit 1
  fi
  # RW stage gone

  # Basic RO check
  if [ -d "${pkgdir}-${target_pkgver}" ]; then
    check_pkgver=$(awk '/^%VERSION%$/ { getline; print $0 }' "${pkgdir}-${target_pkgver}/desc" )
    if [ "$check_pkgver" = "$target_pkgver" ]; then
      # TODO: Do TODO
      echo 'Done'
      exit 0
    fi
  fi

  echo 'Failed wtf'
  exit 1

fi