Promotion by Technology

[fatherbushido]

Promotion component have a RequiredXP element. That one is a non negative integer. Currently we can use a tech to replace it by 0.

The effect of setting RequiredXP to 0 is :

1. promote the current units (see Promotion) (with entity mod)
2. construct the (more) promoted unit instead of the original unit (ref r14388) (with template mod)

That is used to promote a unit with a tech (see for example mace_champion_infantry_a to mace_champion_infantry_e).

But that is not fully flexible : for example one can perhaps want :

• that unit never promote with xp (see old ugly workaround with a 99999 requiredXP
• allow a promotion only when a given tech is researched

So if we want that Promotion allows that, i suggest (for example), to separate 1. and 2. by adding an optional RequiredTechnology in the Promotion template (which would be checked Promotion) and an optional boolean AllowPromotedUnitProduction in the Promotion template (which would be checked in ProductionQueue)