Git OverlayIconManager: avoid removing the overlay icons belonging to other version control systems.

src/AddIns/VersionControl/GitAddIn/Src/OverlayIconManager.cs

@@ -136,7 +136,13 @@ namespace ICSharpCode.GitAddIn
 			
 			WorkbenchSingleton.SafeThreadAsyncCall(
 				delegate {
-					node.Overlay = GetImage(status);
+					Image image = GetImage(status);
+					if (image != null) {
+						node.Overlay = image;
+					} else if (node.Overlay != null && (node.Overlay.Tag as Type) == typeof(GitAddIn.OverlayIconManager)) {
+						// reset overlay to null only if the old overlay belongs to the OverlayIconManager
+						node.Overlay = null;
+					}
 				});
 		}
 		
@@ -196,6 +202,7 @@ namespace ICSharpCode.GitAddIn
 					g.DrawImage(statusImages, destRect, srcRect, GraphicsUnit.Pixel);
 					//g.DrawLine(Pens.Black, 0, 0, 7, 10);
 				}
+				smallImage.Tag = typeof(GitAddIn.OverlayIconManager);
 				statusIcons[index] = smallImage;
 			}
 			return statusIcons[index];