Merge branch 'jl/maint-submodule-recurse-fetch'

Merge branch 'jl/maint-submodule-recurse-fetch'

"git fetch" that recurses into submodules on demand did not check if
it needs to go into submodules when non branches (most notably, tags)
are fetched.

By Jens Lehmann
* jl/maint-submodule-recurse-fetch:
  submodules: recursive fetch also checks new tags for submodule commits