4987 - support `browse_trace` tool in SubX

I've extracted it into a separate binary, independent of my Mu prototype.

I also cleaned up my tracing layer to be a little nicer. Major improvements:

- Realized that incremental tracing really ought to be the default.
  And to minimize printing traces to screen.

- Finally figured out how to combine layers and call stack frames in a
  single dimension of depth. The answer: optimize for the experience of
  `browse_trace`. Instructions occupy a range of depths based on their call
  stack frame, and minor details of an instruction lie one level deeper
  in each case.

Other than that, I spent some time adjusting levels everywhere to make
`browse_trace` useful.

1 files changed, 1 insertions, 1 deletions

diff --git a/057immutable.cc b/057immutable.cc
index d1f1df71..e1feac7a 100644
--- a/057immutable.cc
+++ b/057immutable.cc
@@ -344,7 +344,7 @@ void check_immutable_ingredients(const recipe_ordinal r) {
   //   b) we never call 'put' or 'put-index' on it, and
   //   c) any non-primitive recipe calls in the body aren't returning it as a product
   const recipe& caller = get(Recipe, r);
-  trace(9991, "transform") << "--- check mutability of ingredients in recipe " << caller.name << end();
+  trace(101, "transform") << "--- check mutability of ingredients in recipe " << caller.name << end();
   if (!caller.has_header) return;  // skip check for old-style recipes calling next-ingredient directly
   for (int i = 0;  i < SIZE(caller.ingredients);  ++i) {
     const reagent& current_ingredient = caller.ingredients.at(i);