200   $ try -- '-a-b-c-' # complains

   200 

   201   hg: parse error at 7: not a prefix: end

   201 names that should be caught by fallback mechanism

   202   [255]

   202 

   203   $ log -a-b-c- # succeeds with fallback

   203   $ try -- '-a-b-c-'

   204   (negate

   205     ('symbol', 'a-b-c-'))

   206   * set:

   207   <baseset [4]>

   208   4

   209   $ log -a-b-c-