some trivial(?) questions about packagegroups

["Robert P. J. Day" <rpjday@crashcourse.ca>]

  what should be easy questions about packagegroups, inspired by my
running across some puzzling packagegroup recipes in my travels
recently. (i'll start with examples out of oe-core).

  first, as with any other recipe, given a "trivial" packagegroup
like, say, packagegroup-core-eclipse-debug.bb:

  SUMMARY = "Remote debugging tools for Eclipse integration"

  inherit packagegroup

  RDEPENDS_${PN} = "\
    gdbserver \
    tcf-agent \
    openssh-sftp-server \
    "

there is no need to add a "PROVIDES" line since every recipe file
automatically provides its own name. so far, so good.

  if we move up to packagegroup-core-nfs.bb, note how this recipe file
defines two additional packagegroups, and has to add a PROVIDES line
in order to make those new names accessible:

  PROVIDES = "${PACKAGES}"
  PACKAGES = "${PN}-server ${PN}-client"

  SUMMARY_${PN}-client = "NFS client"
  RDEPENDS_${PN}-client = "nfs-utils-client"

  SUMMARY_${PN}-server = "NFS server"
  RDEPENDS_${PN}-server = "\
    nfs-utils \
    nfs-utils-client \
    "

so the question is, must one supply a PROVIDES line for any
packagegroup names above and beyond the one that comes with the recipe
file itself? i ask what seems like a dumb question as i've run across
packagegroup recipe files that define multiple additional
packagegroups, but do not add them to the PROVIDES line. what is that
supposed to represent?

rday