lua: ability to SetBranchText.

doesn't make much sense to add text to existing branches from lua, but highly useful to set some text to a new branch.
and we also have a default branch text variable now.

BizHawk.Client.Common/movie/tasproj/TasMovie.cs

@@ -85,6 +85,7 @@ namespace BizHawk.Client.Common
 		public TasMovieMarkerList Markers { get; set; }
 		public bool BindMarkersToInput { get; set; }
 		public bool UseInputCache { get; set; }
+		public string NewBranchText = "";
 		public int CurrentBranch { get; set; }
 		public int BranchCount { get { return Branches.Count; } }
 		public TasBranch GetBranch(int index)

BizHawk.Client.EmuHawk/tools/Lua/Libraries/EmuLuaLibrary.Tastudio.cs

@@ -37,6 +37,22 @@ namespace BizHawk.Client.EmuHawk
 			return GlobalWin.Tools.Has<TAStudio>(); // TODO: eventually tastudio should have an engaged flag
 		}
 
+		[LuaMethodAttributes(
+			"setbranchtext",
+			"adds the given message to the existing branch, or to the branch that will be created next if branch index is not specified"
+			)]
+		public void SetBranchText(string text, int? index = null)
+		{
+			if (index != null)
+			{
+				Tastudio.CurrentTasMovie.GetBranch(index.Value).UserText = text;
+			}
+			else
+			{
+				Tastudio.CurrentTasMovie.NewBranchText = text;
+			}
+		}
+
 		[LuaMethodAttributes(
 			"getmarker",
 			"returns the marker text at the given frame, or an empty string if there is no marker for the given frame"

BizHawk.Client.EmuHawk/tools/TAStudio/BookmarksBranchesBox.cs

@@ -116,6 +116,7 @@ namespace BizHawk.Client.EmuHawk
 		public void Branch()
 		{
 			TasBranch branch = CreateBranch();
+			Movie.NewBranchText = ""; // reset every time it's used
 			Movie.AddBranch(branch);
 			BranchView.RowCount = Movie.BranchCount;
 			Movie.CurrentBranch = Movie.BranchCount - 1;
@@ -149,7 +150,7 @@ namespace BizHawk.Client.EmuHawk
 				ChangeLog = new TasMovieChangeLog(Movie),
 				TimeStamp = DateTime.Now,
 				Markers = Movie.Markers.DeepClone(),
-				UserText = ""
+				UserText = Movie.NewBranchText
 			};
 		}