Stop including non-versioned files in the build input (to skip heavy files in datasets)

guix.scm

@@ -3,6 +3,7 @@
                                                   python-nltk
                                                   python-seaborn))
              (guix gexp)
+             (guix git-download)
              ((guix licenses) #:select (lgpl3+))
              (guix packages)
              (guix build-system python))
@@ -15,7 +16,7 @@
     (source
       (local-file %source-dir
                   #:recursive? #t
-                  #:select? (lambda (x . _) (not (string=? (basename x) ".git")))))
+                  #:select? (git-predicate %source-dir)))
     (build-system python-build-system)
     (propagated-inputs
       (list python-matplotlib