There will be about 1h of downtime on 2020-03-02 at 13:00 UTC+1 (change of servers and upgrade to Heptapod 0.20.0 final)

Repository loading: returning proper error if not found

We already had good enough error responses for the case when
the *storage* is not found, but it was missing for the case
when the repository is not found in an existing storage.

This is important, because it can actually break the landing page
of some users: the Rails application does not seem to expect an
unspecified Gitaly error here, but it should recover from
NOT_FOUND.

I've been impaired by this on dev setup after
with some repository removals, but don't have anything of that
kind on hand any more, which would be more reassuring.

We could have a better separation in concerns, as the
subsequent change in `RepositoryExists()` indicates, but that's
not a blocker for the imminent release.
4 jobs for topic/default/repo-not-found in 1 minute and 31 seconds (queued for 1 second)
Status Job ID Name Coverage
  Main
passed #118994
tests-current

00:00:45

100.0%
 
  Compat
passed #118995
check-sdist

00:00:18

passed #118997
tests-hg-default

00:00:38

100.0%
passed #118996
tests-hg-stable

00:00:45

100.0%