backout: don't assume that tip as what we just committed Differential Revision: https://phab.mercurial-scm.org/D9256

url: do not continue HTTP authentication with user=None (issue6425) I initially thought this is a py3-compat bug of passwordmgr._writedebug(), but actually returning (None, str) pair is wrong at all. HTTP authentication would continue with user="None" in that case. Since registering a password of user=None should also be wrong, this patch simply adds early return.