pull after grace

Before pulling, a node waits one measured round trip to the announcer
(1 s at most) and pulls only what is still missing.  If the round trip
isn't known yet, it pulls at once, as now.  On the clean benchmark links
the round trip is a few milliseconds, so those scenarios shouldn't
change.

1 files changed, 3 insertions, 1 deletions

diff --git a/docs/peers.md b/docs/peers.md
index 8b58df0..8a3333d 100644
--- a/docs/peers.md
+++ b/docs/peers.md
@@ -287,7 +287,9 @@ writes go on and newer changes are still on their way to it; nor is a neighbour
 own announcement or STATUS brought them, are this node's: announcements wait 200 to
 400 ms, at random, so of two neighbours with the same news one is usually first, and
 the other skips it), and a neighbour that lacks those heads pulls them (it sets them as the peer's heads in its sync state, so Automerge asks
-for what's missing). It pulls from one neighbour at a time (15 s timeout); neighbours
+for what's missing), if it still lacks them after a round trip to the announcer (at
+most 1 s): while writes go on, the newest are usually on their way to it along a
+writer's tree, and would otherwise come twice. It pulls from one neighbour at a time (15 s timeout); neighbours
 that announce heads it lacks meanwhile wait their turn and are pulled from as soon as
 the current pull is answered, if they still have something it lacks. The regular
 STATUS (every third keepalive) triggers the same pull, so gaps close within a few