[PATCH v5 6/6] doc: add documentation for the proc-receive hook

[Jiang Xin <worldhello.net@gmail.com>]

From: Jiang Xin <zhiyou.jx@alibaba-inc.com>

Add documentation for the new "proc-receive" hook.

Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
---
 Documentation/githooks.txt | 70 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
index 3dccab5375..10ea5c1f18 100644
--- a/Documentation/githooks.txt
+++ b/Documentation/githooks.txt
@@ -333,6 +333,76 @@ The default 'update' hook, when enabled--and with
 `hooks.allowunannotated` config option unset or set to false--prevents
 unannotated tags to be pushed.
 
+[[proc-receive]]
+proc-receive
+~~~~~~~~~~~~
+This hook is invoked by linkgit:git-receive-pack[1] when it reacts to
+special `git push` command.  According to refnames of the commands which
+`git push` sends to 'git-receive-pack', the commands will be devided
+into two groups by matching what the `receive.procReceiveRefs`
+configuration variable defines.  One group of the commands will execute
+the internal `execute_commands` function to update the corresponding
+refnames, and the other group of commands which have matching refnames
+will execute this 'proc-receive' hook to create pull requests, etc.
+If there is no `receive.procReceiveRefs` settings, this hook won't
+execute at all, and all commands are sent to the internal
+`execute_commands` function.
+
+Its exit status only determines the success or failure of the group of
+commands with special refnames, unless atomic push is in use.
+
+This hook executes once for the receive operation.  It takes no
+arguments, but will talk a protocol in pkt-line format with the
+'receive-pack' for reading commands, push-options (optional), and
+sending result.  In the following example, The letter "S" stands for
+"receive-pack" and letter "H" stands for the hook.
+
+    # Version and capabilities negotiation.
+    S: PKT-LINE(version=1\0push-options atomic...)
+    S: flush-pkt
+    H: PKT-LINE(version=1\0push-options...)
+    H: flush-pkt
+
+    # Send commands from server to the hook.
+    S: PKT-LINE(old-oid new-oid ref)
+    S: ... ...
+    S: flush-pkt
+    # Only if push-options have been negotiated.
+    S: PKT-LINE(push-option)
+    S: ... ...
+    S: flush-pkt
+
+    # Receive result from the hook.
+    # OK, run this command successfully.
+    H: PKT-LINE(old-oid new-oid ref ok)
+    # NO, I reject it.
+    H: PKT-LINE(old-oid new-oid ref ng reason)
+    # OK, but use an alternate reference.
+    H: PKT-LINE(old-oid new-oid ref ok ref:alt-ref)
+    # It will fallthrough to receive-pack to execute.
+    H: PKT-LINE(old-oid new-oid ref ft)
+    H: ... ...
+    H: flush-pkt
+
+The "proc-receive" hook may update one or more references, and will send
+its result one by one in pkt-line format.  Each line of the result has
+four fields and one optional message field, like "<old-oid> <new-oid>
+<ref> <status> [<message>]".
+
+The first three fields are the same as those of the commands for
+"receive-pack".
+
+The forth field has a two-letter status code.  Available status codes:
+
+* ok: The command runs successfully.  If the optional message has a
+  prefix "ref:", the hook has created/updated an alternate reference
+  instead.
+
+* ng: Fail to run the command.  Error message is given in the optional
+  message field.
+
+* ft: Will fallthrough to receive-pack to execute.
+
 [[post-receive]]
 post-receive
 ~~~~~~~~~~~~
-- 
2.26.0.4.g39bcdcb101.dirty