Merge branch 'jk/submodule-c-credential' into js/http-custom-headers

* jk/submodule-c-credential: submodule: stop sanitizing config options submodule: use prepare_submodule_repo_env consistently submodule--helper: move config-sanitizing to submodule.c submodule: export sanitized GIT_CONFIG_PARAMETERS t5550: break submodule config test into multiple sub-tests t5550: fix typo in $HTTPD_URL 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