Merge branch 'lx/submodule-clear-variables'

The "git submodule" command did not initialize a few variables it
internally uses and was affected by variable settings leaked from
the environment.

* lx/submodule-clear-variables:
  git-submodule.sh: setup uninitialized variables

diff --cc git-submodule.sh
index 89f915cae99b12d134aeb7e72ec460dfe1e8e247,aba3e109a4aef6e2ada47b4a51639522104f07f3..08e0439df0a2cccf62274c9636e8eeb609827d2f
--- 1/git-submodule.sh
--- 2/git-submodule.sh
+++ b/git-submodule.sh
@@@ -47,7 -47,8 +47,9 @@@ custom_name
  depth=
  progress=
  dissociate=
 +single_branch=
+ jobs=
+ recommend_shallow=
  
  die_if_unmatched ()
  {