[fine] Clean up comments a bit

fine/tests/example_tests.rs

@@ -2,13 +2,13 @@ use fine::parser::concrete::Tree;
 use pretty_assertions::assert_eq;
 
 fn rebase_concrete(source_path: &str, dump: &str) {
-    // RE-BASE
     let contents = std::fs::read_to_string(source_path)
         .expect(&format!("unable to read input file {}", source_path));
 
     let mut result = String::new();
     let mut lines = contents.lines();
 
+    // Search for the "concrete:" section.
     let mut found_concrete_section = false;
     while let Some(line) = lines.next() {
         result.push_str(line);
@@ -26,6 +26,8 @@ fn rebase_concrete(source_path: &str, dump: &str) {
         );
     }
 
+    // We've found the section we care about, replace all the lines we care
+    // about with the actual lines.
     let mut replaced_output = false;
     while let Some(line) = lines.next() {
         if line.starts_with("// | ") {