esv.el: improve documentation

esv.el

@@ -64,20 +64,19 @@
 
 (defun esv (book verses)
   "Fetch the Bible passage identified by BOOK and VERSES.
-The result will be redirected to a buffer specified by `esv-buffer'."
+The result will be redirected to a buffer specified by `esv-buffer'.
+
+Requires the esv command line tool to be in the system's PATH.
+esv can be acquired at <https://sr.ht/~jeremy/esv>."
   (interactive "MBook: \nMVerses: ")
   (let ((buffer (concat book " " verses)))
     (catch 'buffer-exists
       (when (get-buffer buffer)
         (message "Buffer `%s' already exists" buffer)
         (throw 'buffer-exists nil))
-      ;; execute esv
       (call-process esv-program nil buffer t
-        ;; arguments
         (format "-l%d" esv-columns) book verses)
-      ;; display buffer in another window
       (display-buffer buffer)
-      ;; move point to the beginning of the buffer
       (with-current-buffer buffer
         (esv-mode)
         (goto-char (point-min)))