Summary of changes

• Bring in improvement to client certificate handling on Windows from winhttp: support optional client cert #5384
• Commit.prototype.parent() now correctly assigns the repo property on the retrieved commit. This should solve certain bugs when working with a commit retrieved from parent.

Merged PRs into NodeGit

• Bring in Libgit2 #5384 to NodeGit
• Fix behavior of Commit#parent
• Remove DiffList
• Remove unnecessary assignment of Commit#repo

Merged PRs into LibGit2

• winhttp: support optional client cert #5384
• Support core.longpaths on Windows #5347
• Parallelize checkout_create_the_new for perf #4205