throw LibGit2SharpException or repo.Head.TIp==null while parallel

Updated. Code simplified

// use LibGit2Sharp.0.16.0.0 from nuget
// https://github.com/torvalds/linux
var gitpath = @"path/to/linux/source";

var times = 10;
for (int i = 0; i < times; i++)
{
    Task.Run(() =>
    {
        using (var repo = new Repository(gitpath))
        {
            // sometimes throw LibGit2SharpException here
            // An exception of type 'LibGit2Sharp.LibGit2SharpException' occurred in LibGit2Sharp.dll but was not handled in user code
            // Additional information: An error was raised by libgit2. Category = Os (Error).
            // Failed to mmap. No data written: Not enough storage is available to process this command.
            foreach (var commit in repo.Commits)
            {
            }
        }
    });
}

while (true)
{
    using (var repo = new Repository(gitpath))
    {
        // sometimes repo.Head.Tip == null
        repo.Head.Tip.ToString();
    }
}

先使用 Repository(gitpath)、repo.Commits 和 repo.Head.Tip 进行并行复现，然后使用 LibGit2Sharp 0.16.0.0 在 Linux repository 上运行。调查并发构造或访问 repository 是否会导致 mmap 失败和 null tip；当报告的并行操作不再产生这两种现象中的任何一种时，即视为完成；如果项目有合适的测试位置，则添加 regression test。