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
try:
import coverage
if hasattr(coverage, 'process_startup'):
coverage.process_startup()
except ImportError:
pass