Add versioning to difficulty calculators

osu.Game.Rulesets.Catch/Difficulty/CatchDifficultyCalculator.cs

@@ -25,6 +25,8 @@ public class CatchDifficultyCalculator : DifficultyCalculator
 
         private float halfCatcherWidth;
 
+        public override int Version => 20220701;
+
         public CatchDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
             : base(ruleset, beatmap)
         {

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyCalculator.cs

@@ -31,6 +31,8 @@ public class ManiaDifficultyCalculator : DifficultyCalculator
         private readonly bool isForCurrentRuleset;
         private readonly double originalOverallDifficulty;
 
+        public override int Version => 20220701;
+
         public ManiaDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
             : base(ruleset, beatmap)
         {

osu.Game.Rulesets.Osu/Difficulty/OsuDifficultyCalculator.cs

@@ -25,6 +25,8 @@ public class OsuDifficultyCalculator : DifficultyCalculator
         private const double difficulty_multiplier = 0.0675;
         private double hitWindowGreat;
 
+        public override int Version => 20220701;
+
         public OsuDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
             : base(ruleset, beatmap)
         {

osu.Game.Rulesets.Taiko/Difficulty/TaikoDifficultyCalculator.cs

@@ -26,6 +26,8 @@ public class TaikoDifficultyCalculator : DifficultyCalculator
         private const double colour_skill_multiplier = 0.01;
         private const double stamina_skill_multiplier = 0.021;
 
+        public override int Version => 20220701;
+
         public TaikoDifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
             : base(ruleset, beatmap)
         {

osu.Game/Rulesets/Difficulty/DifficultyCalculator.cs

@@ -34,6 +34,11 @@ public abstract class DifficultyCalculator
         private readonly IRulesetInfo ruleset;
         private readonly IWorkingBeatmap beatmap;
 
+        /// <summary>
+        /// A yymmdd version which is used to discern when reprocessing is required.
+        /// </summary>
+        public virtual int Version => 0;
+
         protected DifficultyCalculator(IRulesetInfo ruleset, IWorkingBeatmap beatmap)
         {
             this.ruleset = ruleset;