3101 - purge .traces/ dir from repo history

I'd been toying with this idea for some time now given how large the
repo had been growing. The final straw was noticing that people cloning
the repo were having to wait *5 minutes*! That's not good, particularly
for a project with 'tiny' in its description. After purging .traces/
clone time drops to 7 seconds in my tests.

Major issue: some commits refer to .traces/ but don't really change
anything there. That could get confusing :/

Minor issues:

a) I've linked inside commits on GitHub like a half-dozen times online
or over email. Those links are now liable to eventually break. (I seem
to recall GitHub keeps them around as long as they get used at least
once every 60 days, or something like that.)

b) Numbering of commits is messed up because some commits only had
changes to the .traces/ sub-directory.

13 files changed, 17 insertions, 50 deletions

diff --git a/003trace.cc b/003trace.cc
index 2481c0be..23fd8781 100644
--- a/003trace.cc
+++ b/003trace.cc
@@ -181,22 +181,19 @@ ostream& operator<<(ostream& os, unused end) {
 
 #define DUMP(label)  if (Trace_stream) cerr << Trace_stream->readable_contents(label);
 
-// All scenarios save their traces in the repo, just like code. This gives
-// future readers more meat when they try to make sense of a new project.
-static string Trace_dir = ".traces/";
-string Trace_file;
+bool Save_trace = false;
 
 // Trace_stream is a resource, lease_tracer uses RAII to manage it.
 struct lease_tracer {
   lease_tracer() { Trace_stream = new trace_stream; }
   ~lease_tracer() {
     if (!Trace_stream) return;  // in case tests close Trace_stream
-    if (!Trace_file.empty()) {
-      ofstream fout((Trace_dir+Trace_file).c_str());
+    if (Save_trace) {
+      ofstream fout("last_trace");
       fout << Trace_stream->readable_contents("");
       fout.close();
     }
-    delete Trace_stream, Trace_stream = NULL, Trace_file = "";
+    delete Trace_stream, Trace_stream = NULL;
   }
 };
 
diff --git a/010vm.cc b/010vm.cc
index 8599b74d..198244e4 100644
--- a/010vm.cc
+++ b/010vm.cc
@@ -434,8 +434,7 @@ void dump_memory() {
 }
 
 //:: Helpers for converting various values to string
-//: Use to_string() in trace(), and try to avoid relying on unstable codes that
-//: will perturb .traces/ from commit to commit.
+//: Use to_string() in trace(), and try to keep it stable from run to run.
 //: Use debug_string() while debugging, and throw everything into it.
 //: Use inspect() only for emitting a canonical format that can be parsed back
 //: into the value.
diff --git a/011load.cc b/011load.cc
index 3f273d74..3a65586b 100644
--- a/011load.cc
+++ b/011load.cc
@@ -336,7 +336,6 @@ def main [
 //: this test we can't represent with a scenario
 :(code)
 void test_parse_comment_terminated_by_eof() {
-  Trace_file = "parse_comment_terminated_by_eof";
   load("recipe main [\n"
        "  a:number <- copy 34\n"
        "]\n"
diff --git a/020run.cc b/020run.cc
index 228c8e2d..5568b2a4 100644
--- a/020run.cc
+++ b/020run.cc
@@ -134,7 +134,7 @@ inline const vector<instruction>& routine::steps() const {
 //: Step 1: load all .mu files with numeric prefixes (in order)
 :(before "End Load Recipes")
 // Load .mu Core
-//? Trace_file = "interactive";
+//? Save_trace = true;
 //? START_TRACING_UNTIL_END_OF_SCOPE;
 load_file_or_directory("core.mu");
 //? DUMP("");
@@ -168,7 +168,7 @@ save_snapshots();
 if (!Run_tests && contains_key(Recipe_ordinal, "main") && contains_key(Recipe, get(Recipe_ordinal, "main"))) {
   // Running Main
   setup();
-//?   Trace_file = "interactive";
+//?   Save_trace = true;
 //?   START_TRACING_UNTIL_END_OF_SCOPE;
   trace(9990, "run") << "=== Starting to run" << end();
   assert(Num_calls_to_transform_all == 1);
@@ -201,8 +201,8 @@ void dump_profile() {
 
 :(code)
 void cleanup_main() {
-  if (!Trace_file.empty() && Trace_stream) {
-    ofstream fout((Trace_dir+Trace_file).c_str());
+  if (Save_trace && Trace_stream) {
+    ofstream fout("interactive");
     fout << Trace_stream->readable_contents("");
     fout.close();
   }
diff --git a/029tools.cc b/029tools.cc
index c9700752..108fa0ed 100644
--- a/029tools.cc
+++ b/029tools.cc
@@ -179,8 +179,8 @@ case _SAVE_TRACE: {
 }
 :(before "End Primitive Recipe Implementations")
 case _SAVE_TRACE: {
-  if (!Trace_file.empty()) {
-    ofstream fout((Trace_dir+Trace_file).c_str());
+  if (Save_trace) {
+    ofstream fout("last_trace");
     fout << Trace_stream->readable_contents("");
     fout.close();
   }
diff --git a/050scenario.cc b/050scenario.cc
index 8a9a57d4..b177cab9 100644
--- a/050scenario.cc
+++ b/050scenario.cc
@@ -145,7 +145,6 @@ void run_mu_scenario(const scenario& s) {
   bool not_already_inside_test = !Trace_stream;
 //?   cerr << s.name << '\n';
   if (not_already_inside_test) {
-    Trace_file = s.name;
     Trace_stream = new trace_stream;
     setup();
   }
@@ -161,12 +160,13 @@ void run_mu_scenario(const scenario& s) {
   // End Mu Test Teardown
   if (not_already_inside_test && Trace_stream) {
     teardown();
-    ofstream fout((Trace_dir+Trace_file).c_str());
-    fout << Trace_stream->readable_contents("");
-    fout.close();
+    if (Save_trace) {
+      ofstream fout("last_trace");
+      fout << Trace_stream->readable_contents("");
+      fout.close();
+    }
     delete Trace_stream;
     Trace_stream = NULL;
-    Trace_file = "";
   }
   Current_scenario = NULL;
 }
diff --git a/056shape_shifting_recipe.cc b/056shape_shifting_recipe.cc
index 62da296f..ead3296e 100644
--- a/056shape_shifting_recipe.cc
+++ b/056shape_shifting_recipe.cc
@@ -685,8 +685,6 @@ $error: 0
 :(code)
 // this one needs a little more fine-grained control
 void test_shape_shifting_new_ingredient_does_not_pollute_global_namespace() {
-  Trace_file = "shape_shifting_new_ingredient_does_not_pollute_global_namespace";
-
   // if you specialize a shape-shifting recipe that allocates a type-ingredient..
   transform("def barz x:_elem [\n"
             "  local-scope\n"
diff --git a/091run_interactive.cc b/091run_interactive.cc
index 59c17312..f1647c59 100644
--- a/091run_interactive.cc
+++ b/091run_interactive.cc
@@ -123,8 +123,6 @@ void run_code_begin(bool should_stash_snapshots) {
   if (should_stash_snapshots)
     stash_snapshots();
   Save_trace_stream = Trace_stream;
-  Save_trace_file = Trace_file;
-  Trace_file = "";
   Trace_stream = new trace_stream;
   Trace_stream->collect_depth = App_depth;
 }
@@ -135,7 +133,6 @@ void run_code_end() {
   delete Trace_stream;
   Trace_stream = Save_trace_stream;
   Save_trace_stream = NULL;
-  Trace_file = Save_trace_file;
   Save_trace_file.clear();
   Recipe.erase(get(Recipe_ordinal, "interactive"));  // keep past sandboxes from inserting errors
   if (!Recipe_snapshot_stash.empty())
diff --git a/Readme.md b/Readme.md
index 623ed55b..8081ee69 100644
--- a/Readme.md
+++ b/Readme.md
@@ -313,12 +313,6 @@ c) Try running the tests:
   $ ./mu test
   ```
 
-You might also want to peek in the `.traces` directory, which automatically
-includes logs for each test showing you just how it ran on my machine. If Mu
-eventually gets complex enough that you have trouble running examples, these
-logs might help figure out if my system is somehow different from yours or if
-I've just been insufficiently diligent and my documentation is out of date.
-
 d) Try out the programming environment:
 
   ```shell
diff --git a/git_log_filtered b/git_log_filtered
index 0ca96fdf..e896cabd 100755
--- a/git_log_filtered
+++ b/git_log_filtered
@@ -5,4 +5,4 @@
 #   $ git config alias.ll '!./git_log_filtered'
 #   $ git ll --stat
 
-git log $* -- . ":(exclude)html" ":(exclude).traces"
+git log $* -- . ":(exclude)html"
diff --git a/sandbox/Readme.md b/sandbox/Readme.md
index 5a6d6336..f2cb2fd9 100644
--- a/sandbox/Readme.md
+++ b/sandbox/Readme.md
@@ -18,7 +18,3 @@ either side to run the sandbox.
 
 Known issues: you have to explicitly save inside your editor before hitting
 F4, unlike with 'mu edit'.
-
-One problem with a fork of the edit/ app is that many of the tests write to
-the same files under the .traces/ directory. I try to always commit the
-results of edit/ rather than the sandbox/ app, but I haven't been perfect.
diff --git a/tangle/003tangle.cc b/tangle/003tangle.cc
index 086cca23..ff9aa56e 100644
--- a/tangle/003tangle.cc
+++ b/tangle/003tangle.cc
@@ -300,7 +300,6 @@ list<Line>::iterator balancing_curly(list<Line>::iterator curr) {
 // Remember to update is_input below if you add to this format.
 void emit_test(const string& name, list<Line>& lines, list<Line>& result) {
   result.push_back(Line("void test_"+name+"() {", front(lines).filename, front(lines).line_number-1));  // use line number of directive
-  result.push_back(Line("  Trace_file = \""+name+"\";", front(lines).filename, front(lines).line_number-1));
   while (!lines.empty()) {
     while (!lines.empty() && starts_with(front(lines).contents, "% ")) {
       result.push_back(Line("  "+front(lines).contents.substr(strlen("% ")), front(lines)));
diff --git a/tangle/003tangle.test.cc b/tangle/003tangle.test.cc
index 0c7b94f3..9c8c4040 100644
--- a/tangle/003tangle.test.cc
+++ b/tangle/003tangle.test.cc
@@ -170,7 +170,6 @@ void test_tangle_supports_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: xyz\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -182,7 +181,6 @@ void test_tangle_ignores_empty_lines_in_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: xyz\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -201,7 +199,6 @@ void test_tangle_supports_configurable_toplevel() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  foo(\"abc def\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqr\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -216,7 +213,6 @@ void test_tangle_can_hide_warnings_in_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  Hide_warnings = true;");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: xyz\");");  lines.pop_front();
@@ -229,7 +225,6 @@ void test_tangle_supports_strings_in_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc \\\"def\\\"\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: \\\"xyz\\\"\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -241,7 +236,6 @@ void test_tangle_supports_strings_in_scenarios2() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc \\\"\\\"\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: \\\"\\\"\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -253,7 +247,6 @@ void test_tangle_supports_multiline_input_in_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n  efg\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer2: \\\"\\\"\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -265,7 +258,6 @@ void test_tangle_supports_reset_in_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CLEAR_TRACE;");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"efg\\n\");");  lines.pop_front();
@@ -279,7 +271,6 @@ void test_tangle_can_check_for_absence_at_end_of_scenarios() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n  efg\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqr\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_DOESNT_CONTAIN(\"layer1: xyz\");");  lines.pop_front();
@@ -292,7 +283,6 @@ void test_tangle_can_check_for_absence_at_end_of_scenarios2() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n  efg\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_DOESNT_CONTAIN(\"layer1: pqr\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_DOESNT_CONTAIN(\"layer1: xyz\");");  lines.pop_front();
@@ -305,7 +295,6 @@ void test_tangle_can_check_for_count_in_scenario() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n  efg\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_COUNT(\"layer1\", 2);");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "}");  lines.pop_front();
@@ -317,7 +306,6 @@ void test_tangle_can_handle_mu_comments_in_scenario() {
   list<Line> lines;
   tangle(in, lines);
   CHECK_EQ(lines.front().contents, "void test_does_bar() {");  lines.pop_front();
-  CHECK_EQ(lines.front().contents, "  Trace_file = \"does_bar\";"); lines.pop_front();
   CHECK_EQ(lines.front().contents, "  run(\"abc def\\n# comment1\\n  efg\\n  # indented comment 2\\n\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_CONTENTS(\"layer1: pqrlayer1: xyz\");");  lines.pop_front();
   CHECK_EQ(lines.front().contents, "  CHECK_TRACE_DOESNT_CONTAIN(\"layer1: z\");");  lines.pop_front();