Explicitly set random seed for shuffles

Now the random generator used for shuffling sections (when that is enabled, as
it is by default) a random seed is set explicitly to make sure that shuffles are
predictable. Using the pangamebook filter twice on the same input-file to
generate two different output formats (e.g. PDF and EPUB of the same gamebook)
should now always create two output files with sections in the same order.

It is possible to set the random seed to any number using the gamebook-randomseed
metadata. That should normally not be needed.

README.md

@@ -7,7 +7,7 @@ known use-case is to create a classic [gamebook](https://en.wikipedia.org/wiki/G
 Pandoc and Pangamebook should run on most modern computers. It has been tested
 on desktop computers running Windows 10, Linux (Lubuntu and Debian) and FreeBSD
 13.0. Also on a Raspberry Pi 4 running Raspberry Pi OS and on an Android phone
-(in Termux).
+(in Termux). Tested versions of Pandoc include 2.9.2.1 and 3.0.
 
 (TBD: Test in OSX.)
 
@@ -98,10 +98,10 @@ Name                   Type     Default     Description
 gamebook-numbers       boolean  true        Replace section names with numbers
 gamebook-post-link     string   ''          Text to add after every link
 gamebook-pre-link      string   ''          Text to add before every link
+gamebook-randomseed    integer  2023        Set random seed for shuffle
 gamebook-shuffle       boolean  true        Shuffle sections
 gamebook-strong-links  boolean  true        Use strong text style for links
 
-
 # Gamebook Graph (Graphviz DOT)
 The Pandoc filter *pangamebookdot.lua* is included to create a plain-text
 DOT file from a generated gamebook, that can then be used with the *dot*
@@ -186,7 +186,7 @@ mirror that is updated with new releases.
 # LICENSE
 MIT License
 
-Copyright (c) 2021-2022 Pelle Nilsson
+Copyright (c) 2021-2023 Pelle Nilsson
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

pangamebook.lua

@@ -1,10 +1,10 @@
 -- pandoc filter to turn headers and links into numbers
--- Copyright 2021-2022 Pelle Nilsson
+-- Copyright 2021-2023 Pelle Nilsson
 -- MIT License
 -- source: https://github.com/lifelike/pangamebook
 
--- version: 1.4.0 (2022-08-13)
--- fossil hash: 26a5a109f73c864b55ff771891a8156d8167e0e3d1fbcb2f9a537a4a34bc3364
+-- version: 1.5.0 (2023-01-20)
+-- fossil hash: f223851d094c9358feefd5c0a5a74506c98fdb14873dfab5afc23664a326ea87
 
 local nr = 1
 local mapped = {}
@@ -145,6 +145,15 @@ function Pandoc(doc)
   link_post = from_meta_string(doc.meta, "gamebook-post-link", "")
 
   if from_meta_bool(doc.meta, "gamebook-shuffle", true) then
+     local seed_number = 2023
+     local metadata_seed = doc.meta["gamebook-randomseed"]
+     if metadata_seed ~= nil then
+        local metadata_seed_number = tonumber(seed)
+        if metadta_seed_number ~= nil then
+           seed_number = metadta_seed_number
+        end
+     end
+     math.randomseed(seed_number)
      return pandoc.Pandoc(shuffle_blocks(doc), doc.meta)
   else
      return doc

pangamebookdot.lua

@@ -3,8 +3,8 @@
 -- MIT License
 -- source: https://github.com/lifelike/pangamebook
 
--- version: 1.4.0 (2022-08-13)
--- fossil hash: 26a5a109f73c864b55ff771891a8156d8167e0e3d1fbcb2f9a537a4a34bc3364
+-- version: 1.5.0 (2023-01-20)
+-- fossil hash: f223851d094c9358feefd5c0a5a74506c98fdb14873dfab5afc23664a326ea87
 
 function one_string_from_block(b)
    local result = ""