ambrevar/file: Add match-date< and match-date> helpers.

.local/share/common-lisp/source/ambrevar/file.lisp

@@ -133,3 +133,13 @@ Without PREDICATES, list all files."
 Without PREDICATES, list all files."
   (let ((*finder-include-directories* nil))
     (apply #'walk root predicates)))
+
+(defun match-date< (timestamp)
+  "Return a file predicate that matches on modification time #'< than timestamp."
+  (lambda (file)
+    (local-time:timestamp< (modification-date file) timestamp)))
+
+(defun match-date> (timestamp)
+  "Return a file predicate that matches on modification time #'> than timestamp."
+  (lambda (file)
+    (local-time:timestamp> (modification-date file) timestamp)))