Add a new "ORDER:" map header for sorting game-mode maps.

The first step towards fixing #7383.  Defaults to INT_MAX, so things
that do not set it explicitly will be last.  If two maps have the
same ORDER:, they will be sorted by description/name as before.

Also change the des cache index format to store ORDER (necessitating a
minor version bump).  Rather than leaving ORDER at its default value
when loading an des cache index from earlier versions, we throw out
the entire index so that it can be regenerated.

1 files changed, 2 insertions, 0 deletions

diff --git a/crawl-ref/source/mapdef.h b/crawl-ref/source/mapdef.h
index 47ed0d32de..05d89a1dfb 100644
--- a/crawl-ref/source/mapdef.h
+++ b/crawl-ref/source/mapdef.h
@@ -1102,6 +1102,8 @@ public:
     string          name;
     // Description for the map that can be shown to players.
     string          description;
+    // Order among related maps; used only for tutorial/sprint/zotdef.
+    int             order;
     string          tags;
     depth_ranges    place;