update dirs to use argparse

share/functions/dirs.fish

@@ -1,15 +1,20 @@
 function dirs --description 'Print directory stack'
-    # process options
-    if set -q argv[1]
-        switch $argv[1]
-            case -c
-                # clear directory stack
-                set -e -g dirstack
-                return 0
-        end
+    set -l options 'h/help' 'c'
+    argparse -n dirs --max-args=0 $options -- $argv
+    or return
+
+    if set -q _flag_help
+        __fish_print_help dirs
+        return 0
     end
 
-    # replace $HOME with ~
+    if set -q _flag_c
+        # Clear directory stack.
+        set -e -g dirstack
+        return 0
+    end
+
+    # Replace $HOME with ~.
     string replace -r '^'"$HOME"'($|/)' '~$1' -- $PWD $dirstack | string join " "
     echo
 end