changegroup: don't run changegroup hooks if nodes are gone The changegroup hook runs when the repo lock is released, but it's possible that multiple transactions have happened during that single lock and therefore the commits the hook was for may be gone. This is the case in the shelve extension where it adds a commit and strips it in the same lock but different transactions (which results in warning messages during unshelve on hgsubversion repos). A real fix would be to attach the hook to the transaction instead, but that might have unknown consequences. Since we're this close to code-freeze, this fix just prevents the hook from running if the commit disappeared.