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.
Issue351: mq: qrefresh can create extra revlog entry
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo b > b
$ hg ci -A -m foo
adding b
$ echo cc > b
$ hg qnew -f foo.diff
$ echo b > b
$ hg qrefresh
$ hg debugindex b
rev linkrev nodeid p1 p2
0 0 1e88685f5dde 000000000000 000000000000