Re: [PATCH 3/3] Use /dev/null for update hook stdin.

"Shawn O. Pearce" [off-list ref] writes:

Currently the update hook invoked by receive-pack has its stdin
connected to the pushing client.  The hook shouldn't attempt to
read from this stream, and doing so may consume data that was
meant for receive-pack.  Instead we should give the update hook
/dev/null as its stdin, ensuring that it always receives EOF and
doesn't disrupt the protocol if it attempts to read any data.

Both 2 and 3 look sane, but can we have a few new tests too?