Sync with Git 2.14.4

* maint-2.14:
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

diff --cc submodule-config.c
Simple merge