protocol-capabilities.txt: document symref
In
7171d8c15f ("upload-pack: send symbolic ref information as
capability"), we added a symref capability to the pack protocol, but it
was never documented. Adapt the patch notes from that commit and add
them to the capabilities documentation.
While we're at it, add a disclaimer to the top of
protocol-capabilities.txt noting that the doc only applies to v0/v1 of
the wire protocol.
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>