pull: only prefetch bookmarks when using bundle1 All bundle2 servers now support the 'listkeys' part(1), so we'll always be able to fetch bookmarks data at the same time as the changeset. This should be enough to avoid the one race condition that this bookmark prefetching is trying to work around. It even allows future server to make sure everything is generated from the same "transaction" if they become capable of such. The current code was already overwriting the prefetched value with the one in bundle2 anyway. Note that this is not preventing all race conditions in related to bookmark in 'hg pull' it makes nothing better and nothing worse. Reducing the number of listkeys calls will reduce the latency on pull. The pre-fetch is also moved into a discovery step because it seems to belong there. (1) Because all servers not speaking 'pushkey' parts are compatible with the 'HG2X' protocol only.

pull: document the race condition with bookmark name It seems valuable to document this in-place to help the next poor soul looking at this code to understand what kind of beast he is currently facing.