Separate updatedAt from mtime in SaveDetails

If a new save is added to the saves list of an instance the current save
selected to be loaded by default changes its state without updating the
mtime of the file on disk, which in turn means basing the updatedAt
property on mtime will not work with caching.  Fix by having a separate
updatedAt property that is set by the controller whenever the save
details changes from the controller's perspective.

Noticed-By: @Cooldude2606

packages/controller/src/HostConnection.ts

@@ -269,12 +269,14 @@ export default class HostConnection extends BaseConnection {
 	}
 
 	async handleInstanceSaveDetailsUpdatesEvent(event: lib.InstanceSaveDetailsUpdatesEvent) {
+		const now = Date.now();
 		const updates: lib.SaveDetails[] = [];
 		for (const save of event.updates) {
 			const existingSave = this._controller.saves.get(save.id);
 			if (existingSave && save.equals(existingSave)) {
 				continue;
 			}
+			save.updatedAt = now;
 			this._controller.saves.set(save.id, save);
 			updates.push(save);
 		}
@@ -283,6 +285,7 @@ export default class HostConnection extends BaseConnection {
 			for (const [id, save] of this._controller.saves) {
 				if (save.instanceId === event.instanceId && !updatedSaves.has(id)) {
 					save.isDeleted = true;
+					save.updatedAt = now;
 					updates.push(save);
 					this._controller.saves.delete(id);
 				}

packages/host/src/Instance.ts

@@ -402,6 +402,7 @@ rcon.print(game.table_to_json(players))`.replace(/\r?\n/g, " ");
 				stat.mtimeMs,
 				name === loadedSave,
 				name === defaultSave,
+				0, // Set by controller
 				false,
 			));
 		}

packages/lib/src/data/messages_instance.ts

@@ -290,6 +290,8 @@ export class SaveDetails {
 		public mtimeMs: number,
 		public loaded: boolean,
 		public loadByDefault: boolean,
+		/** Millisecond Unix timestamp this entry was last updated at */
+		public updatedAt: number,
 		public isDeleted: boolean,
 	) { }
 
@@ -301,6 +303,7 @@ export class SaveDetails {
 		"mtimeMs": Type.Number(),
 		"loaded": Type.Boolean(),
 		"loadByDefault": Type.Boolean(),
+		"updatedAt": Type.Number(),
 		"isDeleted": Type.Boolean(),
 	});
 
@@ -313,6 +316,7 @@ export class SaveDetails {
 			json.mtimeMs,
 			json.loaded,
 			json.loadByDefault,
+			json.updatedAt,
 			json.isDeleted,
 		);
 	}
@@ -322,16 +326,16 @@ export class SaveDetails {
 		return `${this.instanceId}/${this.name}`;
 	}
 
-	get updatedAt() {
-		return this.mtimeMs;
-	}
-
 	/**
 	 * Compare this save with another save.
 	 * @param other - save to compare with.
 	 * @returns true if this save is identical to the provided save
 	 */
 	equals(other: SaveDetails) {
+		// Note that updatedAt is not included in the equality check because
+		// instances send the whole list of saves with updatedAt set to zero
+		// to the controller whenever any save changes and this equals check
+		// is used to filter whether a save was updated.
 		return (
 			this.instanceId === other.instanceId
 			&& this.type === other.type