message: reexport revision guard
diff: @@ -21,6 +21,7 @@ use std::fmt::Debug;
  use std::hash::Hash;
  pub use crate::runtime::Runtime;
  +pub use crate::runtime::RevisionGuard;
  /// The base trait which your "query context" must implement. Gives
  /// access to the salsa runtime, which you must embed into your query
  