Merge pull request libgit2#531 from suhaibmujahid/patch-1

Switch over the version constraints to v0.28

Merge pull request libgit2#530 from libgit2/cmn/bump-libgit2-28

Update libgit2 to v0.28.4

Merge pull request libgit2#529 from libgit2/cmn/bump-libgit2-27

Update libgit2 to v0.27.10