[PATCH v5 0/2] reporting transport helper errors

I think this topic is close to being done, so I just wanted to move it
along.

  [1/2]: transport-helper: report errors properly

    This is Felipe's v4 patch with the adjustments I suggested in
    review. It explains more in the commit message, and should fix
    Thomas's valgrind failures (it consumes fast-export's data before
    dying rather than sleeping and hoping that fast-export is done
    writing).

  [2/2]: transport-helper: mention helper name when it dies

    This changes the error message, to help with the issue raised by
    Sverre.

-Peff