setdiscovery: return anyincoming=False when remote's only head is nullid This fixes (issue2907) a crash when using 'hg incoming --bundle' with an empty remote repo and a non-empty local repo. This also fixes an unreported bug that 'hg summary --remote' erroneously reports incoming changes when the remote repo is empty and the local is not. Also, add a test to make sure issue2907 stays fixed