Sync with 2.17.2

* maint-2.17: Git 2.17.2 fsck: detect submodule paths starting with dash fsck: detect submodule urls starting with dash Git 2.16.5 Git 2.15.3 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