shelve: allow multiple shelves with --patch and --stat Before this patch, there was a single way to see multiple shelves using `--patch --list` which show all the shelves. Doing `--patch s1 s2` returns an error. This patch allows to show multiple shelves using `--patch` and `--stat`.

zstd: vendor python-zstandard 0.6.0 Commit 63c68d6f5fc8de4afd9bde81b13b537beb4e47e8 from https://github.com/indygreg/python-zstandard is imported without modifications (other than removing unwanted files). This includes minor performance and feature improvements. It also changes the vendored zstd library from 1.1.1 to 1.1.2. # no-check-commit