A new way to make units invulnerable for debugging

With debug features enabled (the --debug command line switch), select the
unit and type ";unit invulnerable=yes".

This method operates by reducing the opponent's hit chance to zero. As a
result, it doesn't slow down damage calculation unlike the "increase HP
to ridiculous levels" method.

changelog

@@ -82,6 +82,10 @@ Version 1.13.5+dev:
      (extremely high HP, drain, slow, berserk, etc.) it's significantly faster than the
      default damage calculation method.
 * Miscellaneous and bug fixes:
+   * A new way to make units invulnerable for debugging: select the unit and type
+     ";unit invulnerable=yes". This method operates by decreasing the opponent's hit
+     chance to zero: as a result, it doesn't slow down damage prediction unlike the
+     "increase HP to ridiculous levels" method.
    * Fixed a stray ; character appearing pre-entered in the command console.
    * Fixed bug in wesnothd that was causing server crashes if game with
      multiple network and local players was ran.

src/actions/attack.cpp

@@ -156,6 +156,11 @@ battle_context_unit_stats::battle_context_unit_stats(const unit &u,
 		unit_abilities::effect cth_effects(cth_specials, chance_to_hit, backstab_pos);
 		chance_to_hit = cth_effects.get_composite_value();
 
+		if (opp.get_state("invulnerable"))
+		{
+			chance_to_hit = 0;
+		}
+
 		// Compute base damage done with the weapon.
 		int base_damage = weapon->modified_damage(backstab_pos);
 

src/units/unit.cpp

@@ -564,6 +564,11 @@ unit::unit(const config &cfg, bool use_traits, const vconfig* vcfg)
 		hit_points_ = max_hit_points_;
 	}
 
+	if (cfg["invulnerable"].to_bool(false) == true)
+	{
+		set_state("invulnerable", true);
+	}
+
 	goto_.x = cfg["goto_x"].to_int() - 1;
 	goto_.y = cfg["goto_y"].to_int() - 1;