Feature request: Create blobs in-memory

I would like to make a diff between two strings with libgit2sharp. The strings hold file contents loaded elsewhere. The diff.Compare-methods only take blobs, and the constructors of the Blobclass don't accept strings or streams and are marked internal. This prevents me from creating blobs directly. I have to write to disk first.

    var oldFileContents = @"
        Line 1
        Line 2
        Line 3
    ";

    var newFileContents = @"
        Line 1
        Line 2 has changed
    ";

    
    var path = Repository.Init("C:\\tmp");
    var repo = new Repository(path);

    var oldObjectId = repo.ObjectDatabase.Write<Blob>(Encoding.UTF8.GetBytes(oldFileContents));
    var newObjectId = repo.ObjectDatabase.Write<Blob>(Encoding.UTF8.GetBytes(newFileContents));
    var oldBlob = repo.Lookup<Blob>(oldObjectId);
    var newBlob = repo.Lookup<Blob>(newObjectId);
    var diff = repo.Diff.Compare(oldBlob, newBlob);  // Works as expected

    // git repo for in-memory operations
    var in_memory_repo = new Repository();

    // This line failes with the LibGit2SharpException "path cannot exist in repository". As far as I can see this is intentional.
    var in_memory_blob = in_memory_repo.ObjectDatabase.Write<Blob>(Encoding.UTF8.GetBytes(oldFileContents));

Seeing that libgit2sharp already supports working with diffs and patches in-memory, it would be nice to be able to create blobs from strings or streams.

Start by tracing Blob construction, ObjectDatabase.Write, and Diff.Compare in the libgit2sharp API. The requested behavior is to create blobs from strings or streams and pass them to in-memory diffs without writing to disk or requiring a disk-backed repository; validate this with the old and new contents shown in the issue.