Wildcards in gtags' --file option

Hello,

  ls -F shows:  A/ B/ C/ Makefile X/ path.mk

  I want to restrict gtags to the directories and sub-directories
  of B and C.

  Instead of cd'ing to B/ and C/ and running gtags there, would like
  to run once gtags from above both B/ and C/.

  Tried "gtags --file list" with list containing the lines B/* and C/*
  but that does not work.  
  
  So how to specify wildcards for the --file option?
  
  Thanks,
  
  --Suresh