docs: clarify requirements when using command line options with special characters within a shell

src/borg/archiver/help_cmd.py

@@ -101,6 +101,15 @@ class HelpMixIn:
         from within a shell, the patterns should be quoted to protect them from
         expansion.
 
+        Pattern matching special characters, e.g. white space, within a shell may 
+        require adjustments, such as putting quotation marks around the arguments.
+        Example: 
+        Using bash, the following command line option would match and exclude "item name":
+        ``--pattern='-path/item name'``
+        Note that when a pattern file is read directly by borg, e.g. when using 
+        ``--exclude-from`` or ``--patterns-from`, there is no shell involved and thus 
+        no quotation marks are required.
+
         The ``--exclude-from`` option permits loading exclusion patterns from a text
         file with one pattern per line. Lines empty or starting with the hash sign
         '#' after removing whitespace on both ends are ignored. The optional style