tests: demonstrate crash caused by pinning of non-existent mergestate node
If the mergestate somehow contains a reference to a non-existent node,
it causes most commands to crash since
aaeccdb6e654 (repoview: pin
revisions for `local` and `other` when a merge is active,
2020-09-04). This patch adds a test showing that.
Differential Revision: https://phab.mercurial-scm.org/D9077
running: init test1
result: 0
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: 0
running: commit -m commit2 -d 2000-01-02 foo
result: 0
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: 0
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: 0