Add tastudio.get_branch_index_by_id

Author: YoshiRulz

src/BizHawk.Client.EmuHawk/tools/Lua/Libraries/TAStudioLuaLibrary.cs

@@ -403,6 +403,19 @@ public LuaTable GetBranches()
 				indexFrom: 0);
 		}
 
+		[LuaMethodExample("""
+			tastudio.setbranchtext("New label", tastudio.get_branch_index_by_id(branch_id));
+		""")]
+		[LuaMethod(
+			name: "get_branch_index_by_id",
+			description: "Finds the branch with the given UUID (0-indexed). Returns -1 if not found.")]
+		public int GetBranchIndexByID(string id)
+		{
+			if (!Guid.TryParseExact(id, format: "D", out var parsed)) return -1;
+			return Tastudio.CurrentTasMovie.Branches.Index()
+				.FirstOrNull(tuple => tuple.Item.Uuid == parsed)?.Index ?? -1;
+		}
+
 		[LuaMethodExample("local nltasget = tastudio.getbranchinput( \"97021544-2454-4483-824f-47f75e7fcb6a\", 500 );")]
 		[LuaMethod("getbranchinput", "Gets the controller state of the given frame with the given branch identifier")]
 		public LuaTable GetBranchInput(string branchId, int frame)