tests/test-issue1089.t

packaging: add Cosmic and Disco, remove Trusty and Artful

- Trusty was publicly supported until 2019-04-30
- Artful was publicly supported until 2018-07-19
- Cosmic was publicly supported until 2019-07-18
- Disco will be publicly supported until 2020-01

Cosmic is officially out-of-date, but since it still may be in use, and because
we didn't add it when it first came out, I think it would be nice to support it
until the next time somebody decides to update this list of Ubuntu releases.

Differential Revision: https://phab.mercurial-scm.org/D6761

https://bz.mercurial-scm.org/1089

  $ hg init
  $ mkdir a
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ hg ci -m m a

  $ mkdir a b
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ cd b

Relative delete:

  $ hg ci -m m ../a

  $ cd ..