eclipse subprojects confusion

[Gary Aitken]

after cloning the eclipse repo and then doing
  git checkout R4_2_maintenance
  git pull --recurse-submodules
the eclipse submodules are still empty.
i.e. the directory structure looks like:

  .../eclipse.platform.releng.aggregator
      .git
      .gitignore
      .gitmodules
      devutils
        description.txt
        submodule_pull_r42x.sh
      eclipse-platform-parent
        pom.xml
      eclipse.jdt                  (empty dir)
      eclipse.jdt.core             (empty dir)
      <...>
      pom.xml
      <...>

I see the submodule_pull_r42x.sh script that looks like it will populate the
subdirs, but shouldn't the --recurse-submodules do that?

I took a chance and did
  bash devutils/submodule_pull_r42x.sh
which failed with
  rt.equinox.incubator                no such file or directory
then created that subdir,
switched back to r4_2_maintenance
and tried again.

After apparently executing ok, the subdirs are still empty.
Any reason why all those
  cd eclipse.jdt.core ; git checkout R3_8_maintenance ; git pull ; cd ..
things apparently did nothing?

Are the subdirs all totally separate repositories which have to be separately 
set up in git?  Or do I need to manually set them up as submodules?
or???

New to git and the eclipse build structure so likely pretty confused...

Thanks,

Gary