migrator: Allow migrating between different configs of the same driver This was notably a problem with SQL since mod_storage_sql is a single module that connects to different SQL databases. The problem was that since it was already loaded once, the output configuration was not applied and it would have migrated to the origin database. This essentially reloads the module after updating the configuration, which should work with all storage modules as long as everything they need are kept in the 'provider' or driver table.

local data = {}
local getinfo = debug.getinfo;
local function linehook(ev, li)
	local S = getinfo(2, "S");
	if S and S.source and S.source:match"^@" then
		local file = S.source:sub(2);
		local lines = data[file];
		if not lines then
			lines = {};
			data[file] = lines;
			for line in io.lines(file) do
				lines[#lines+1] = line;
			end
		end
		io.stderr:write(ev, " ", file, " ", li, " ", lines[li], "\n");
	end
end
debug.sethook(linehook, "l");