garrison_names={'G0', 'G1', 'G2', 'G3', 'G4', 'G5', 'G6', 'G7', 'G8', 'G9'}
garrisons={}

function pack(...)
  return arg
end

for j, gar in garrison_names do
  Trigger(5, gar, 'capture_gar')
  garrisons[gar] = {}
  local gar_creatures = pack(GetObjectCreaturesTypes(gar))
  for i, creature in gar_creatures do
    if creature ~= 0 then
      garrisons[gar][creature] = GetObjectCreatures(gar, creature)
    end
  end
end

function capture_gar(oldowner, newowner, hero, gar)
  for creature, count in garrisons[gar] do
    if not (creature == 0 or count == 0) then
      garrisons[gar][creature] = count * 2
      AddObjectCreatures(gar, creature, count * 2)
    end
  end
  DenyGarrisonCreaturesTakeAway(gar, 1)
end