[PATCH v2 09/16] pack-protocol.txt: a bit about smart http

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/technical/pack-protocol.txt | 66 +++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index c73b62f..a1672bc 100644
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -551,3 +551,69 @@ An example client/server communication might look like this:
    S: 0018ok refs/heads/debug\n
    S: 002ang refs/heads/master non-fast-forward\n
 ----
+
+Smart HTTP Transport
+--------------------
+
+Smart HTTP protocol is basically "git protocol on top of http". The
+base protocol is modified slightly to fit HTTP processing model: no
+bidirectional full-duplex connections, the program may read the
+request, write a response and must exit.
+
+Reference Discovery
+-------------------
+
+The server end always sends the list of references in both push and
+fetch cases. This ref list is retrieved by the client's sending HTTP
+GET request to a smart http url ending with
+"/info/refs?service=<service>" where <service> could be either
+git-upload-pack or git-receive-pack for fetching or pushing
+respectively. The output is in pkt-line format.
+
+----
+  advertised-refs  =  service
+		      flush-pkt
+		      (no-refs / list-of-refs)
+		      flush-pkt
+
+  service          =  PKT-LINE("# service=" service-name)
+  service-name     =  ("git-upload-pack" / "git-receive-pack")
+
+  no-refs          =  PKT-LINE(zero-id SP "capabilities^{}"
+		      NUL capability-list LF)
+
+  list-of-refs     =  first-ref *other-ref
+  first-ref        =  PKT-LINE(obj-id SP refname
+		      NUL capability-list LF)
+
+  other-ref        =  PKT-LINE(other-tip / other-peeled)
+  other-tip        =  obj-id SP refname LF
+  other-peeled     =  obj-id SP refname "^{}" LF
+
+  capability-list  =  capability *(SP capability)
+  capability       =  1*(LC_ALPHA / DIGIT / "-" / "_")
+  LC_ALPHA         =  %x61-7A
+----
+
+Packfile Negotiation
+--------------------
+
+For fetching, packet negotiation is via a series of HTTP POST requests
+to an url ending with "/git-upload-pack" with the content in pkt-line
+format. git-upload-pack's response consists of a "service" line like
+in Reference Discovery followed by normal git-upload-pack packet
+lines. Capability multi_ack_detailed is required by Smart HTTP.
+
+Common objects that are discovered are appended onto the request as
+have lines and are sent again on the next request. This allows the
+remote side to reinitialize its in-memory list of common objects
+during the next request and the remote does not need to maintain the
+negotiation state.
+
+Reference Update Request
+------------------------
+
+For pushing, a HTTP POST request is sent to an url ending with
+"/git-receive-pack" with the content in pkt-line format.
+git-receive-pack's response consists of a "service" line like in
+Reference Discovery followed by normal git-receive-pack packet lines.
-- 
1.8.2.83.gc99314b