receivepack: Wire proc-receive handler writer to hooks
During the proc-recieve hook, the update and post-receive hook are invoked and incorrectly direct their output the receive-pack RPC stdout and stderr. This results in the hooks ouput not being encapsulated in sideband packets as expected and causes errors.
Instead wire the hooks output to the proc-receive handler which writes to the proc-receive hook stderr. This allows Git to handle parsing the stderr and writing sideband packets automatically.
Related: #6173 (closed)
Edited by Justin Tobler