Merge branch 'cf/submodule-progress-dissociate'

"git submodule update" and "git submodule add" supported the
"--reference" option to borrow objects from a neighbouring local
repository like "git clone" does, but lacked the more recent
invention "--dissociate".  Also "git submodule add" has been taught
to take the "--progress" option.

* cf/submodule-progress-dissociate:
submodule: add --dissociate option to add/update commands
submodule: add --progress option to add command
submodule: clean up substitutions in script

diff --cc Documentation/git-submodule.txt
Simple merge

diff --cc builtin/submodule--helper.c
Simple merge

diff --cc git-submodule.sh
Simple merge

diff --cc t/t7400-submodule-basic.sh
Simple merge