[RFCv2 02/12] Document details of transport function APIs

[Johan Herland <johan@herland.net>]

From: Daniel Barkalow <barkalow@iabervon.org>

In particular, explain which of the fields of struct ref is used for
what purpose in the input to and output from each function.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Johan Herland <johan@herland.net>
---
 transport.h |   38 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/transport.h b/transport.h
index 3cb0abc..b45e6c5 100644
--- a/transport.h
+++ b/transport.h
@@ -18,11 +18,49 @@ struct transport {
 	int (*set_option)(struct transport *connection, const char *name,
 			  const char *value);
 
+	/**
+	 * Returns a list of the remote side's refs. In order to allow
+	 * the transport to try to share connections, for_push is a
+	 * hint as to whether the ultimate operation is a push or a fetch.
+	 *
+	 * If the transport is able to determine the remote hash for
+	 * the ref without a huge amount of effort, it should store it
+	 * in the ref's old_sha1 field; otherwise it should be all 0.
+	 **/
 	struct ref *(*get_refs_list)(struct transport *transport, int for_push);
+
+	/**
+	 * Fetch the objects for the given refs. Note that this gets
+	 * an array, and should ignore the list structure.
+	 *
+	 * If the transport did not get hashes for refs in
+	 * get_refs_list(), it should set the old_sha1 fields in the
+	 * provided refs now.
+	 **/
 	int (*fetch)(struct transport *transport, int refs_nr, struct ref **refs);
+
+	/**
+	 * Push the objects and refs. Send the necessary objects, and
+	 * then tell the remote side to update each ref in the list
+	 * from old_sha1 to new_sha1.
+	 *
+	 * Where possible, set the status for each ref appropriately.
+	 *
+	 * If, in the process, the transport determines that the
+	 * remote side actually responded to the push by updating the
+	 * ref to a different value, the transport should modify the
+	 * new_sha1 in the ref. (Note that this is a matter of the
+	 * remote accepting but rewriting the change, not rejecting it
+	 * and reporting that a different update had already taken
+	 * place)
+	 **/
 	int (*push_refs)(struct transport *transport, struct ref *refs, int flags);
 	int (*push)(struct transport *connection, int refspec_nr, const char **refspec, int flags);
 
+	/** get_refs_list(), fetch(), and push_refs() can keep
+	 * resources (such as a connection) reserved for futher
+	 * use. disconnect() releases these resources.
+	 **/
 	int (*disconnect)(struct transport *connection);
 	char *pack_lockfile;
 	signed verbose : 2;
-- 
1.6.4.rc3.138.ga6b98.dirty