shelve: fix crash on unshelve without .shelve metadata file
Follow up for
c67c94c0e7ae and
38373da1af02.
The inline comment says "we should keep track of the unshelve node in case
we need to reuse it." Perhaps such case isn't tested, and this patch does
NOT add a test for the reuse of the unbundled revision.
Also, I have no idea what should be done if new revision is unbundled
because of "node not in repo".
https://bz.mercurial-scm.org/619
$ hg init
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
adding b
$ hg co -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Fast-forward:
$ hg merge b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -Ammerge
Bogus fast-forward should fail:
$ hg merge b
abort: merging with a working directory ancestor has no effect
[255]
Even with strange revset (issue4465)
$ hg merge ::.
abort: merging with a working directory ancestor has no effect
[255]