In the refactor from 926b9c72f61b5be6bf8d952512f1d0932fbaf898, the error
handling was substantially reworked, and changed the types of errors
returned.
Notably, in the case of a network error, instead of propogating the
error through to return from pushWriter.Write (as previously), it would
be propagated through to pushWriter.Commit - however, this is too late,
since we've already closed the io.Pipe by the time we would have reached
this function. Therefore, we get the generic error message "io:
read/write on closed pipe" for *every network error*.
This patch corrects this behavior to ensure that the correct error
object is always returned as early as possible, by checking the error
result after writing and detecting a closed pipe.
Additionally, we do some additional hardening - specifically we prevent
falling through when resetting the content or detecting errors, and
update the tests to explicitly check for the ErrReset message.
Signed-off-by: Justin Chadwell <me@jedevc.com>