tests: add test showing crash when shelving ghosted rename target When you `hg rename` a file and then delete the rename target, `hg shelve` will give you a traceback. Note that the shelve succeeds and the shelve is correct, it's just the update to the parent that fails (i.e. to the parent of the commit that was created for the shelve). This can be squashed into the next commit if the reviewer prefers. Differential Revision: https://phab.mercurial-scm.org/D8045