Merge branch 'jk/submodule-c-credential'

"git -c credential.<var>=<value> submodule" can now be used to propagate configuration variables related to credential helper down to the submodules. * jk/submodule-c-credential: git_config_push_parameter: handle empty GIT_CONFIG_PARAMETERS git: submodule honor -c credential.* from command line quote: implement sq_quotef() submodule: fix segmentation fault in submodule--helper clone submodule: fix submodule--helper clone usage submodule: check argc count for git submodule--helper clone submodule: don't pass empty string arguments to submodule--helper clone