This allows individual projects to enable clang-format pre-upload hook
without worrying about the paths of the various tools.
Bug: 26800693
Test: Added a PREUPLOAD.cfg in external/minijail, got a warning.
Change-Id: Ia9ee738ad3305934e8e6ca50261f96ca3ab30852
This doesn't turn on anything (yet), just includes some guidelines for
people who are thinking about changing/enabling things.
Bug: 29606287
Test: `repo upload` still works
Change-Id: I397f53aed417fe9bfd1a00dac2d0d5b380f66e10