Barracks can't be built with old savegames

[GunChleoc]

When loading an old savegame (e.g. Build 19) in current trunk, the Barracks isn't added to the list of allowed buildings, turning the games unplayable.

[Notabilis (notabilis27)]

A related message while loading the game:

WARNING: player 1 is allowed to create worker type Recruit but his Headquarters 259 at (11, 53) does not have a next_spawn time set for that worker type; setting it to 132107

(Printed by Warehouse::load_finish().)

I am not sure how to fix this, though. Always enabling the barracks when loading a game is not feasible since that would break campaigns even when saved with the same game version.
The easiest way would be to simply ignore it. Why should anyone load that old saves anyway? ;-)

We also could use the notification above and add a special case if the recruit has not been loaded (Or add a global special case when a pre-barracks save game is loaded. Not sure whether this is possible).
Then we could either revert to the old logic and make soldiers recruitable in the warehouses. However, this might affect games played afterwards when not restarting the program. Or we could enable barracks in this case. This would possibly result in a useless building when an old campaign save game has been loaded but would probably be fine for normal games.

[GunChleoc (gunchleoc)]

We have an allow_buildings function - maybe check if it's < the number of buildings types for the tribe? That would take care of campaigns. We will have to keep non-seafaring maps in mind though, since they disallow ports and shipyards, and the weaving mill for barbarians. So, it might be easier to just add it after all and live with the extra building in the campaigns/scenarios.

I like to keep full savegame compatibility throughout a release cycle, repeatedly breaking it between Builds 18 and 19 was a pain in the butt for bug hunting. I'm planning to break it again after Build 20, just once at the start of the new release cycle.

[Notabilis (notabilis27)]

A possible solution is implemented in the attached branch. I haven't created a merge request yet since I am not that fond of the code. While it works for old saves and for current campaigns it uses hard coded names from the lua files, so when those change the code will break.

If you think this approach is fine, feel free to (request a) merge.

[GunChleoc (gunchleoc)]

The hard coding can be avoided if we add a function barracks() to TribeDescr, just like we have for the headquarters, for example. The definition then goes on the bottom of data/tribes/<tribename>.lua

[Notabilis (notabilis27)]

Do we also add a special type for recruits then? As an alternative we could get them by checking the inputs of the barracks.

[Notabilis (notabilis27)]

Barracks are added as a special building now. The recruit is found by checking the inputs of the barracks.

[GunChleoc (gunchleoc)]

The proposed branch only works with 1 of the attached savegames.

[GunChleoc (gunchleoc)]

Fixed in build20-rc1