Smart HTTP clients may request both multi_ack_detailed and no-done in
the same request to prevent the client from needing to send a "done"
line to the server in response to a server's "ACK %s ready".
For smart HTTP, this can save 1 full HTTP RPC in the fetch exchange,
improving overall latency when incrementally updating a client that
has not diverged very far from the remote repository.
Unfortuantely this capability cannot be enabled for the traditional
bi-directional connections. multi_ack_detailed has the client sending
more "have" lines at the same time that the server is creating the
"ACK %s ready" and writing out the PACK stream, resulting in some race
conditions and/or deadlock, depending on how the pipe buffers are
implemented. For very small updates, a server might actually be able
to send "ACK %s ready", then the PACK, and disconnect before the
client even finishes sending its first batch of "have" lines. This
may cause the client to fail with a broken pipe exception. To avoid
all of these potential problems, "no-done" is restricted only to the
smart HTTP variant of the protocol.
Change-Id: Ie0d0a39320202bc096fec2e97cb58e9efd061b2d
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
b209671d04