Merge branch 'jl/status-added-submodule-is-never-ignored' into maint

Merge branch 'jl/status-added-submodule-is-never-ignored' into maint

"git status" (and "git commit") behaved as if changes in a modified
submodule are not there if submodule.*.ignore configuration is set,
which was misleading.  The configuration is only to unclutter diff
output during the course of development, and should not to hide
changes in the "status" output to cause the users forget to commit
them.

* jl/status-added-submodule-is-never-ignored:
  commit -m: commit staged submodules regardless of ignore config
  status/commit: show staged submodules regardless of ignore config