Add consistent monotonic day counter - get_day_count()

I've written several experimental bits of code that revolve around the
need for a consistent calendar, but implementing one is extremely hard
in mods due to time changes and mods overriding core.get_timeofday(),
which will conflict.

The second part of the problem is that doing this from a mod requires
constant maintenance of a settings file.

An implementation in core is trivial, however, and solves all of
these problems at virtually no cost: No extra branches in server
steps, and a single branch when minetest.set_time_of_day(), which is
entirely reasonable.

We store the day_count value in env_meta.txt.

The use case is obvious: This change allows mods to create an actual
virtual calendar, or properly account for seasonal changes, etc..

We add a "/days" chatcommand that displays the current day count. No
permissions are needed. It can only retrieve the day count, not
modify it.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/script/lua_api/l_env.h b/src/script/lua_api/l_env.h
index 0e385ffef..89dd7978f 100644
--- a/src/script/lua_api/l_env.h
+++ b/src/script/lua_api/l_env.h
@@ -113,6 +113,9 @@ private:
 	// get_gametime()
 	static int l_get_gametime(lua_State *L);
 
+	// get_day_count() -> int
+	static int l_get_day_count(lua_State *L);
+
 	// find_node_near(pos, radius, nodenames) -> pos or nil
 	// nodenames: eg. {"ignore", "group:tree"} or "default:dirt"
 	static int l_find_node_near(lua_State *L);