In commit e642e535f35c2b54a40df808f1fd24584cf0c719 of PR
git-lfs/git-lfs#5169 we dropped support for Debian 9 (stretch) in
our primary Git LFS project, so we drop it here now as well, for
the reasons explained that commit's description:

  Debian 9 (stretch) is now beyond LTS support and on to ELTS support,
  which means that the typical Debian infrastructure is no longer involved
  and updates are no longer available from Debian.  As a result, it's not
  really appropriate for us to continue to build packages on stretch since
  we can't be certain our dependencies or build environment are secure.

  It is the case that some of the OSes that use Debian 9 packages, such as
  some versions of Ubuntu, do still receive security updates, but since we
  don't build specifically for those OSes, we'll need to drop support for
  them as well.  Of the OSes receiving mainline (non-extended) security
  support, only Ubuntu bionic is affected.

In commit git-lfs/git-lfs@e642e53 of
PR git-lfs/git-lfs#5169 we dropped support for Debian 9 (stretch) in
our primary Git LFS project, so we drop it here now as well, for
the reasons explained that commit's description:

  Debian 9 (stretch) is now beyond LTS support and on to ELTS support,
  which means that the typical Debian infrastructure is no longer involved
  and updates are no longer available from Debian.  As a result, it's not
  really appropriate for us to continue to build packages on stretch since
  we can't be certain our dependencies or build environment are secure.

  It is the case that some of the OSes that use Debian 9 packages, such as
  some versions of Ubuntu, do still receive security updates, but since we
  don't build specifically for those OSes, we'll need to drop support for
  them as well.  Of the OSes receiving mainline (non-extended) security
  support, only Ubuntu bionic is affected.

We removed support for CentOS 5 in commit
369c712 of PR git-lfs#4080 and for
CentOS 6 in commit d69e28d in
PR git-lfs#4328; we also removed support for Debian 8 in commit
ff36182 of that same PR git-lfs#4328,
and for Debian 9 in commit e642e53
of PR git-lfs#5169.

We can therefore also remove these distribution names from the
set of patterns we match our package filenames against in our
upload script for Packagecloud when it prints Markdown output
(although this feature of the script may no longer be useful).

We add comments noting the EOL dates for a number of distributions
to our Packagecloud upload script, and also remove a duplicate entry
for SUSE Linux Enterprise Server 12.5 which was added in commit
9ef46f8 of PR git-lfs#5169.

Ubuntu Impish Indri reached its EOL in July 2022, so we remove it
from the list of Debian 11 distributions for which we publish
packages to Packagecloud, and we add Ubuntu Kinetic Kudu to the
Debian 11 list as it was released in October 2022.

Fedora 34 reached its EOL in July 2022 and Fedora 35 reached its
EOL in December 2022, so we remove them from the list of CentOS 8
distributions, and we add Fedora 37 to the Rocky 9 list as it was
released in November 2022.

We add Linux Mint Vera to the list of Debian 11 distributions
as it was released in December 2022.

We remove OpenSUSE 15.3 from the list of CentOS 7 distributions
as it reached its EOL in December 2022.

SUSE Linux Enterprise Server 12 SP4 reached its general EOL
in June 2020, so we remove it now, and SLES 15 SP3 reached its
general EOL in December 2022, so we also remove it now.

Note that we have been somewhat inconsistent in our handling of
SLES 12 and 15 Service Packs, as we have only removed SLES 12
Service Packs once they reached their LTSS (Long Term Service Pack
Support) EOL, while we have removed SLES 15 SPs when they reached
their general EOLs.  Thus we removed SLES 12 SP3 in commit
9ef46f8 of PR git-lfs#5169 when that
Service Pack reached its LTSS EOL, but we removed SLES 15 SP2
in commit e2465f8 PR git-lfs#5010 when
that Service Pack reached its general EOL but not its LTSS EOL,
which is still in the future (December 2024), as is the LTSS EOL
for SLES 15 SP1 (January 2024).

To be more consistent, we assume SLES users have upgraded to
the latest Service Pack within the required six-month period
after its release, and we can drop support for older SPs at
that point.  This is effectively how we have already treated
the earlier SPs for SLES 15, so applying that guideline to
SLES 12 SP4 as well should be reasonable.

Ubuntu Impish Indri reached its EOL in July 2022, so we remove it
from the list of Debian 11 distributions for which we publish
packages to Packagecloud, and we add Ubuntu Kinetic Kudu to the
Debian 11 list as it was released in October 2022.

Fedora 34 reached its EOL in July 2022 and Fedora 35 reached its
EOL in December 2022, so we remove them from the list of CentOS 8
distributions, and we add Fedora 37 to the Rocky 9 list as it was
released in November 2022.

We add Linux Mint Vera to the list of Debian 11 distributions
as it was released in December 2022.

We remove OpenSUSE 15.3 from the list of CentOS 7 distributions
as it reached its EOL in December 2022.

SUSE Linux Enterprise Server 12 SP4 reached its general EOL
in June 2020, so we remove it now, and SLES 15 SP3 reached its
general EOL in December 2022, so we also remove it now.

Note that we have been somewhat inconsistent in our handling of
SLES 12 and 15 Service Packs, as we have only removed SLES 12
Service Packs once they reached their LTSS (Long Term Service Pack
Support) EOL, while we have removed SLES 15 SPs when they reached
their general EOLs.  Thus we removed SLES 12 SP3 in commit
9ef46f8 of PR git-lfs#5169 when that
Service Pack reached its LTSS EOL, but we removed SLES 15 SP2
in commit e2465f8 PR git-lfs#5010 when
that Service Pack reached its general EOL but not its LTSS EOL,
which is still in the future (December 2024), as is the LTSS EOL
for SLES 15 SP1 (January 2024).

To be more consistent, we assume SLES users have upgraded to
the latest Service Pack within the default six-month period
after its release, and we can drop support for older SPs at
that point.  This is effectively how we have already treated
the earlier SPs for SLES 15, so applying that guideline to
SLES 12 SP4 as well should be reasonable.