Merge branch 'jt/upload-pack-error-report' into maint

"git upload-pack", which is a counter-part of "git fetch", did not
report a request for a ref that was not advertised as invalid.
This is generally not a problem (because "git fetch" will stop
before making such a request), but is the right thing to do.

* jt/upload-pack-error-report:
  upload-pack: report "not our ref" to client