TODOTXT_DISABLE_FILTER missing from help text.

Should be in there for consistency; corresponding option is -x.

tests/t0100-code-nobacktick.sh

@@ -5,11 +5,12 @@ test_description='no old-style backtick command substitution
 This test checks the todo.sh script itself for occurrences
 of old-style backtick command substitution, which should be
 replaced with $(...).
+On failure, it will print each offending line number and line.
 '
 . ./test-lib.sh
 
 test_todo_session 'no old-style backtick command substitution' <<EOF
->>> sed -n -e 's/[ \t]#.*//' -e '/\d96/{=;p}' "$(which todo.sh)"
+>>> sed -n -e 's/\(^\|[ \t]\)#.*//' -e '/\`/{' -e '=;p' -e '}' "$(which todo.sh)"
 EOF
 
 test_done

todo.sh

@@ -232,6 +232,7 @@ help()
 		    TODOTXT_PLAIN                   is same as option -p (1)/-c (0)
 		    TODOTXT_DATE_ON_ADD             is same as option -t (1)/-T (0)
 		    TODOTXT_VERBOSE=1               is same as option -v
+		    TODOTXT_DISABLE_FILTER=1        is same as option -x
 		    TODOTXT_DEFAULT_ACTION=""       run this when called with no arguments
 		    TODOTXT_SORT_COMMAND="sort ..." customize list output
 		    TODOTXT_FINAL_FILTER="sed ..."  customize list after color, P@+ hiding
@@ -474,6 +475,7 @@ TODOTXT_AUTO_ARCHIVE=${TODOTXT_AUTO_ARCHIVE:-1}
 TODOTXT_DATE_ON_ADD=${TODOTXT_DATE_ON_ADD:-0}
 TODOTXT_DEFAULT_ACTION=${TODOTXT_DEFAULT_ACTION:-}
 TODOTXT_SORT_COMMAND=${TODOTXT_SORT_COMMAND:-env LC_COLLATE=C sort -f -k2}
+TODOTXT_DISABLE_FILTER=${TODOTXT_DISABLE_FILTER:-}
 TODOTXT_FINAL_FILTER=${TODOTXT_FINAL_FILTER:-cat}
 
 # Export all TODOTXT_* variables