private ObjectId Commit(ObjectWriter ow, DirCache treeB, ObjectId[] parentIds)
{
var c = new Commit(db) { TreeId = treeB.writeTree(ow), Author = new PersonIdent("A U Thor", "a.u.thor", 1L, 0) };
c.Committer = c.Author;
c.ParentIds = parentIds;
c.Message = "Tree " + c.TreeId.Name;
return ow.WriteCommit(c);
}