It started with me fixing a repeated "are are" but the wording was
incomprehensible so I tried to untangle it.
Closes #13921
$! First the files in the original source directory which is assumed to be
$! under source code control are compared with the copy directory.
$!
-$! Then the files are are only in the copy directory are listed.
+$! Only files present in the copy directory are listed.
$!
-$! The result will five diagnostics about of files:
+$! Diagnostics are displayed about the files:
$! 1. Files that are not generation 1.
$! 2. Files missing in the copy directory.
$! 3. Files in the copy directory not in the source directory.