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
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Ama
adding a
$ hg qnew a.patch
$ echo a >> a
$ hg qrefresh
$ hg qnew b.patch
$ echo b > b
$ hg add b
$ hg qrefresh
$ hg qnew c.patch
$ echo c > c
$ hg add c
$ hg qrefresh
$ hg qgoto a.patch
popping c.patch
popping b.patch
now at: a.patch
$ hg qgoto c.patch
applying b.patch
applying c.patch
now at: c.patch
$ hg qgoto b.patch
popping c.patch
now at: b.patch
Using index:
$ hg qgoto 0
popping b.patch
now at: a.patch
$ hg qgoto 2
applying b.patch
applying c.patch
now at: c.patch
No warnings when using index:
$ hg qnew bug314159
$ echo d >> c
$ hg qrefresh
$ hg qnew bug141421
$ echo e >> c
$ hg qrefresh
$ hg qgoto 1
popping bug141421
popping bug314159
popping c.patch
now at: b.patch
$ hg qgoto 3
applying c.patch
applying bug314159
now at: bug314159
Detect ambiguous non-index:
$ hg qgoto 14
patch name "14" is ambiguous:
bug314159
bug141421
abort: patch 14 not in series
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