How can you do mutually exclusive values in zparseopts?

git-remote-url.zsh

#!/bin/zsh

usage () cat <<EOS
usage: ${ZSH_SCRIPT:t:s/-/ /} [-c | -m | -p | -bBRANCH] [file] [start[-end]]

options:
  -c        use the current branch
  -m        use the master branch [default]
  -p        get a permalink
  -bBRANCH  use BRANCH

Prints out a link to the repo, optoinally to 'file' (or a range of lines in it)
EOS

set -- -c -bfoo -p -bbar # Test data

# Parse options
zparseopts -D -- \
  {c,m,p,b:}=opts \
  h=help

# :-( It's not `-c -p -b bar`
print -- $opts #=> -c -b bar -p