test: Add a check for too long or badly reflowed docstrings

This ensures that docstring comments are wrapped to 80 chars. ffrank
seemed to be making this mistake far too often, and it's a silly thing
to look for manually. As it turns out, I've made it too, as have many
others. Now we have a test that checks for most cases. There are still a
few stray cases that aren't checked automatically, but this can be
improved upon if someone is motivated to do so.

Before anyone complains about the 80 character limit: this only checks
docstring comments, not source code length or inline source code
comments. There's no excuse for having docstrings that are badly
reflowed or over 80 chars, particularly if you have an automated test.

lang/interfaces/metadata.go

@@ -225,9 +225,9 @@ func ParseMetadata(reader io.Reader) (*Metadata, error) {
 	return metadata, nil
 }
 
-// FindModulesPath returns an absolute path to the Path dir where modules can
-// be found. This can vary, because the current metadata file might not specify
-// a Path value, meaning we'd have to return the global modules path.
+// FindModulesPath returns an absolute path to the Path dir where modules can be
+// found. This can vary, because the current metadata file might not specify a
+// Path value, meaning we'd have to return the global modules path.
 // Additionally, we can search upwards for a path if our metadata file allows
 // this. It searches with respect to the calling base directory, and uses the
 // ParentPathBlock field to determine if we're allowed to search upwards. It

lang/interfaces/unification.go

@@ -24,8 +24,8 @@ import (
 )
 
 // Invariant represents a constraint that is described by the Expr's and Stmt's,
-// and which is passed into the unification solver to describe what is known
-// by the AST.
+// and which is passed into the unification solver to describe what is known by
+// the AST.
 type Invariant interface {
 	// TODO: should we add any other methods to this type?
 	fmt.Stringer