ENH: adjust completion parser

- restrict to text between "^[Oo]ptions:" and "-help-full" to avoid
  potential issues when more text is introduced in the usage output.

etc/config.sh/bash_completion

@@ -139,14 +139,16 @@ _of_complete_()
         #   -opt2 <arg>   descrip
         #   -help-full
         # Ignore -help-man (internal option).
-        # Terminate parsing on first appearance of -help-full
+        # Begin parsing after first appearance of "^[Oo]ptions:"
+        # Terminate parsing on first appearance of "-help-full"
         # - options with '=' (eg, -mode=ugo) are not handled very well at all.
         # - alternatives (eg, -a, -all) are not handled nicely either,
         #   for these treat ',' like a space to catch the worst of them.
         if [ -z "$choices" ]
         then
             local helpText=$($appName -help-full 2>/dev/null | \
-                sed -ne 's/^ *//; /^$/d; /^[^-]/d; /^--/d; /^-help-man/d;' \
+                sed -ne '1,/^[Oo]ptions:/d' \
+                    -e 's/^ *//; /^$/d; /^[^-]/d; /^--/d; /^-help-man/d;' \
                     -e 'y/,/ /; s/=.*$/=/;' \
                     -e '/^-[^ ]* </{ s/^\(-[^ ]* <\).*$/\1/; p; d }' \
                     -e 's/^\(-[^ ]*\).*$/\1/; p; /^-help-full/q;' \