City HP and RCS: How do they work?

[vyyt]

Can we get a rundown of how city hit points/strength and ranged attack work now?

• How do the numbers apply in a unit vs city combat? And where do they come from?
• How do the garrisoned units add to the numbers? (there are reports on GitHub that units increase and sometimes even decrease the city RCS - which they should not?)
• How do the defensive buildings affect the numbers?

I know some people like cities 1-shoting units, while others prefer substantial marginal damage and some extremist would even remove the city RCS altogether. Same with city hitpoints, some people prefer long sieges, some say a city without a garrison should fall in 1 melee attack. And then there is the balance against land and naval.

PS: For those of you who have been altering the city RCS with CITY_RANGED_ATTACK_STRENGTH_MULTIPLIER, it seems it has stopped working when the new city HP/RCS calculation system was introduced. Already reported to GitHub.