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

From: Daniel Barkalow <barkalow@xxxxxxxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Johan Herland <johan@xxxxxxxxxxx>
---
 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

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