Add test submodules to make raco test clean.

Author: samth

commit.rkt

@@ -54,4 +54,8 @@
   (write-bytes #"\n" o)
   (close-output-port o)
 
-  (subprocess-wait p))
+  (subprocess-wait p)
+
+  ;; to avoid raco test failures
+  (module test racket)
+  )

main.rkt

@@ -47,3 +47,5 @@
 (define end-time (chop:go dest-dir tmp-dir dry-run?))
 
 (printf "\n### git-slice: finished in ~a total seconds\n" (/ (- end-time init-time) 1000.))
+
+(module test racket)

prune.rkt

@@ -108,4 +108,7 @@
     (lambda (o) (fprintf o "~a\npost: ~s\n" commit keeps))
     'append)
 
+  ;; to avoid raco test failures
+  (module test racket)
+
   )