Merge pull request libgit2#4983 from libgit2/ethomson/v0_28_1

Release v0.28.1

Merge pull request libgit2#4970 from libgit2/ethomson/0_28

v0.28 rc1

Merge pull request libgit2#4970 from libgit2/ethomson/0_28

v0.28 rc1

CHANGELOG: there's changes (plural) not just one

Merge pull request libgit2#4846 from pks-t/pks/v0.27.6

Bugix release v0.27.7

Merge pull request libgit2#4866 from pks-t/pks/v0.27.6-security

Release v0.27.6

Merge pull request libgit2#4865 from pks-t/pks/v0.26.8

Release v0.26.8

Merge pull request libgit2#4834 from pks-t/pks/v0.27.5

Security release v0.27.5

Merge pull request libgit2#4835 from pks-t/pks/v0.26.7

Security release v0.26.7

Merge pull request libgit2#4756 from pks-t/pks/v0.27.4

Release v0.27.4