Add brief documentation on how to change the rg-menu

docs/configuration.org

@@ -512,4 +512,46 @@
   :PROPERTIES:
   :CUSTOM_ID: customizing_the_menu
   :END:
-  Please refer to the [[https://magit.vc/manual/transient/Modifying-Existing-Transients.html#Modifying-Existing-Transients][transient]] documentation for customizing the menu.
+  The menu can be modified from the emacs configuration file.
+
+  To add a new *switch* before the option triggered by =-n= at suffix
+  level 3:
+  #+BEGIN_SRC elisp
+    (transient-insert-suffix 'rg-menu "-n" '(3 "-o" "Only print matches" "--only-matching"))
+  #+END_SRC
+  To add a new *option* before the option triggered by =-g= at suffix
+  level 4:
+  #+BEGIN_SRC elisp
+    (transient-insert-suffix 'rg-menu "-g" '(4 "-f" "Pattern file" "--file="))
+  #+END_SRC
+  The === in =--file== triggers argument input for the flag.
+
+  To remove an item from the menu specify the trigger key in the
+  transient remove command.
+  For example, to remove the =Search hidden files= switch use the following:
+  #+BEGIN_SRC elisp
+    (transient-remove-suffix 'rg-menu "-h")
+  #+END_SRC
+
+  Please refer to the [[https://magit.vc/manual/transient/Modifying-Existing-Transients.html#Modifying-Existing-Transients][transient]] documentation for details on customizing the menu.
+
+  This package also adds a convenience function for appending new
+  *commands* to the menu in the groups at the bottom.
+
+  :FUNCTION:
+  #+BEGIN_SRC elisp :results value raw :exports results
+  (rg-function-info 'rg-menu-transient-insert)
+  #+END_SRC
+  This inserts a new command under =group= if it exists, otherwise a
+  new group is created. =key=, =description= and =command= is as for
+  the =transient-insert-suffix= function.
+
+  For example to insert a new command under =Search= group:
+  #+BEGIN_SRC elisp
+    (rg-menu-transient-insert "Search" "m" "My search" 'my-search-command)
+  #+END_SRC
+
+  It's usually better to use the =:menu= key of the [[func:rg-define-search]]
+  macro to define a search function and adding it to the menu in one go.
+  :END:
+