Git merge base

git-merge-base

Find two commits common ancestor

Git

$ git merge-base oneCommit secondCommit

LibGit2Sharp

public string GetMergeBase(string a, string b)
{
    using (var repo = new Repository("path/to/your/repo"))
    {
        var aCommit = Repository.Commits.First(c => c.Sha == a);
        var bCommit = Repository.Commits.First(c => c.Sha == b);
        return repo .Commits.FindCommonAncestor(aCommit, bCommit).Sha;
    }
}