Merge branch 'sp/push-sideband'

* sp/push-sideband:
receive-pack: Send internal errors over side-band #2
t5401: Use a bare repository for the remote peer
receive-pack: Send hook output over side band #2
receive-pack: Wrap status reports inside side-band-64k
receive-pack: Refactor how capabilities are shown to the client
send-pack: demultiplex a sideband stream with status data
run-command: support custom fd-set in async
run-command: Allow stderr to be a caller supplied pipe

diff --cc Documentation/technical/api-run-command.txt
Simple merge