shelve: always backup shelves instead of deleting them Instead of being deleted, shelve files are now moved into the .hg/shelve-backup directory. This is designed similarly to how strip saves backups into .ht/strip-backup. The goal is to prevent data loss especially when using unshelve. There are cases in which a user can complete an unshelve but lose some of the data that was shelved by, for example, resolving merge conflicts incorrectly. Storing backups will allow the user to recover the data that was shelved, at the expense of using more disk space over time.