I recently made a package (see wip/qcad-partlibrary) that includes an
empty directory named brown&sharpe.

make print-PLIST outputs an @exec ${MKDIR} line for the empty directory
brown&sharpe, but this fails in pkg_add because & is a shell metacharacter.

I don't see it documented (for either print-PLIST or pkg_*) just what the
intended quoting/escaping conventions are for PLIST entries, but if the
conventions were documented it would be possible to make sure all the tools
were using the same ones.  :)

-Chap