tests/test-purge-ignored-directory.t

rust: update `clap` to the latest 4.x version

This brings in more up-to-date dependencies, some bug fixes (none of which are
relevant yet), and slightly improved compile times.

skip ignored directories if -i or --all not specified

  $ hg init t
  $ cd t
  $ echo 'ignored' > .hgignore
  $ hg ci -qA -m init -d'2 0'
  $ mkdir ignored
  $ ls
  ignored
  $ hg purge -v --no-confirm
  $ ls
  ignored