Clojure script: find duplicate filenames in a nested directory structure

find-m-files.clj

(ns find-m-files
  (:import java.io.File))

; Wrap java.io.file methods
(defn is-file? [f] (.isFile f))
(defn is-dir? [f] (.isDirectory f))
(defn get-name [f] (.getName f))
(defn get-path [f] (.getPath f))

(defn get-m-files [d]
    "Recursively get a list of File objects for files ending in .m in the given directory"
    (let [ls (if (is-dir? d) (.listFiles d) nil)
          files (filter is-file? ls)
          dirs (filter is-dir? ls)]
      (if (nil? ls)
        nil
        (flatten (concat
          (filter (fn [f] (re-matches #".*\.m" (get-name f))) files) ; .m files
          (map get-m-files dirs))))))

(defn dupes [s]
  "Get a list of the duplicate elements in [s]. That list may itself contain duplicates."
  (cond
    (empty? s) nil ; Break recursion
    (> (.indexOf (rest s) (first s)) -1) (cons (first s) (dupes (rest s)))
    true (recur (rest s))))

(defn duplicate-filenames [d]
  "Get a list of the paths to all filenames that are duplicated in the given directory."
  (let [files (get-m-files (File. d))
        names (map get-name files)
        duped-names (set (dupes names))
        duped-files (filter (fn [f] (contains? duped-names (get-name f))) files)]
    (map get-path
      (sort #(compare (get-name %1) (get-name %2)) duped-files))))