Add World.New(parent, path) method

src/gaemstone.ECS/EntityRef.cs

@@ -50,14 +50,17 @@ public unsafe class EntityRef
 		=> ecs_delete(World, this);
 
 	public EntityBuilder NewChild(EntityPath? path = null)
-		=> World.New(EnsureRelativePath(path)).ChildOf(this);
+		=> World.New(this, EnsureRelativePath(path));
 	public EntityRef? LookupChild(EntityPath path)
 		=> World.LookupByPath(this, EnsureRelativePath(path)!);
 	public EntityRef LookupChildOrThrow(EntityPath path)
 		=> World.LookupByPathOrThrow(this, EnsureRelativePath(path)!);
 
 	private static EntityPath? EnsureRelativePath(EntityPath? path)
-		{ if (path?.IsAbsolute == true) throw new ArgumentException("path must not be absolute", nameof(path)); return path; }
+	{
+		if (path?.IsAbsolute == true) throw new ArgumentException(
+			$"Path '{path}' must not be absolute", nameof(path)); return path;
+	}
 
 
 	public EntityRef? Parent

src/gaemstone.ECS/World.cs

@@ -33,14 +33,28 @@ public unsafe partial class World
 	public void Dispose()
 		=> ecs_fini(this);
 
+
 	public EntityBuilder New(EntityPath? path = null)
 		=> new(this, path);
 
+	public EntityBuilder New(EntityRef? parent, EntityPath? path = null)
+	{
+		var entity = New(path);
+		// If given path is absolute, the new entity won't be created as a
+		// child of the specified parent. Alternatively, EntityRef.NewChild
+		// can be used, which will throw when an absolute path is given.
+		if ((path?.IsRelative != false) && (parent != null))
+			entity.ChildOf(parent);
+		return entity;
+	}
+
+
 	public bool Progress(TimeSpan delta)
 		=> ecs_progress(this, (float)delta.TotalSeconds);
 
 	public void Quit()
 		=> ecs_quit(this);
 
+
 	public static implicit operator ecs_world_t*(World w) => w.Handle;
 }