doc: desc +/- value prefix for opts/configs in man

Author: xdelaruelle

doc/source/module.rst

@@ -410,6 +410,9 @@ switches are accepted:
  The order of the elements in *LIST* does not matter. Module names are the
  only content reported when *LIST* is set to an empty value.
 
+ *LIST* may be prefixed by ``+`` or ``-`` character to indicate respectively
+ to append it to or subtract it from current configuration option value.
+
  See also :envvar:`MODULES_AVAIL_OUTPUT` and :envvar:`MODULES_LIST_OUTPUT`.
 
  .. only:: html
@@ -423,6 +426,9 @@ switches are accepted:
        Elements *variant* and *variantifspec* added for :subcmd:`avail`
        sub-command
 
+    .. versionchanged:: 5.3
+       Prefixes ``+`` and ``-`` added to append and subtract elements
+
 .. option:: --paginate
 
  Pipe all message output into :command:`less` (or if set, to the command
@@ -734,6 +740,10 @@ Module Sub-Commands
  If no value is currently set for an option *name*, the mention ``<undef>`` is
  reported.
 
+ For options whose value is a colon-separated list, *value* may be prefixed by
+ ``+`` or ``-`` character. It indicates respectively to append it to or
+ subtract it from current option value.
+
  When command-line switch ``--dump-state`` is passed, current
  :file:`modulecmd.tcl` state and Modules-related environment variables are
  reported in addition to currently set :file:`modulecmd.tcl` options.
@@ -1425,6 +1435,10 @@ Module Sub-Commands
 
     .. versionadded:: 4.3
 
+    .. versionchanged:: 5.3
+       *Value* prefixes ``+`` and ``-`` added to append and subtract elements
+       to list-value options
+
 .. subcmd:: display modulefile...
 
  Display information about one or more *modulefiles*. The display sub-command