File patchdockerfile of Package build

#!/usr/bin/perl -w

################################################################
#
# Copyright (c) 2020 SUSE Linux Products GmbH
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or 3 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program (see the file COPYING); if not, write to the
# Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#
################################################################

use strict;
use warnings;

my $install_docker_support = "COPY .obs-docker-support /usr/local/sbin/obs-docker-support\n" .
                             "RUN obs-docker-support --install\n";
my $uninstall_docker_support = "RUN obs-docker-support --uninstall\n";

my @sections = ( [] );
while (<STDIN>) {
  $_ .= "\n" unless /\n$/s;
  push @sections, [] if /^FROM\s/i;
  push @{$sections[-1]}, $_;
}

# write out header unmodified
print join('', @{shift @sections});

for my $s (@sections) {
  # cannot use docker support for scratch images
  if (@$s && $s->[0] =~ /^\s*[fF][rR][oO][mM]\s+scratch[\s\n]/) {
    print join('', @$s);
    next;
  }
  # do not install docker support if no RUN is used
  # (we always do it for the last stage to get the basepackage list)
  if ($s != $sections[-1] && !grep {/^\s*RUN/i} @$s) {
    print join('', @$s);
    next;
  }
  # analyze the section (first line is always FROM)
  my ($install_idx, $uninstall_idx, $from_scratch);
  my $idx = 0;
  for my $line (@$s) {
    if ($line =~ /^[uU][sS][eE][rR]\s+root[\s\n]/) {
      $install_idx = $idx unless defined $install_idx;
      $uninstall_idx = undef;
    } elsif ($line =~ /^[uU][sS][eE][rR]\s+/) {
      $install_idx = 0 unless defined $install_idx;
      $uninstall_idx = $idx unless defined $uninstall_idx;
    }
    $idx++;
  }
  # patch in docker support commands
  $s->[$install_idx || 0] .= $install_docker_support;
  substr($s->[$uninstall_idx], 0, 0, $uninstall_docker_support) if defined $uninstall_idx;
  $s->[-1] .= $uninstall_docker_support unless defined $uninstall_idx;
  print join('', @$s);
}