Merge branch 'pk/subsub-fetch-fix'

"git fetch" did not work correctly with nested submodules where the
innermost submodule that is not of interest got updated in the
upstream, which has been corrected.

* pk/subsub-fetch-fix:
  submodules: fix of regression on fetching of non-init subsub-repo

diff --cc t/t5526-fetch-submodules.sh
Simple merge