[PATCH 2/6] fetch-pack: truly stop negotiation upon ACK ready

[Jonathan Tan <jonathantanmy@google.com>]

When "ACK %s ready" is received, find_common() clears rev_list in an
attempt to stop further "have" lines from being sent [1]. This appears
to work, despite the invocation to mark_common() in the "while" loop.
Though it is possible for mark_common() to invoke rev_list_push() (thus
making rev_list non-empty once more), it is more likely that the commits
in rev_list that have un-SEEN parents are also unparsed, meaning that
mark_common() is not invoked on them.

To avoid all this uncertainty, it is better to explicitly end the loop
when "ACK %s ready" is received instead of clearing rev_list. Remove the
clearing of rev_list and write "if (got_ready) break;" instead.

The corresponding code for protocol v2 in process_acks() does not have
the same problem, because the invoker of process_acks()
(do_fetch_pack_v2()) proceeds immediately to processing the packfile
upon "ACK %s ready". The clearing of rev_list here is thus redundant,
and this patch also removes it.

[1] The rationale is further described in the originating commit
f2cba9299b ("fetch-pack: Finish negotation if remote replies "ACK %s
ready"", 2011-03-14).

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 fetch-pack.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 1358973a4..2d090f612 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -517,10 +517,8 @@ static int find_common(struct fetch_pack_args *args,
 					mark_common(commit, 0, 1);
 					retval = 0;
 					got_continue = 1;
-					if (ack == ACK_ready) {
-						clear_prio_queue(&rev_list);
+					if (ack == ACK_ready)
 						got_ready = 1;
-					}
 					break;
 					}
 				}
@@ -530,6 +528,8 @@ static int find_common(struct fetch_pack_args *args,
 				print_verbose(args, _("giving up"));
 				break; /* give up */
 			}
+			if (got_ready)
+				break;
 		}
 	}
 done:
@@ -1281,7 +1281,6 @@ static int process_acks(struct packet_reader *reader, struct oidset *common)
 		}
 
 		if (!strcmp(reader->line, "ready")) {
-			clear_prio_queue(&rev_list);
 			received_ready = 1;
 			continue;
 		}
-- 
2.17.0.768.g1526ddbba1.dirty