As described in native gits file "git-read-tree.txt" git has in a
special mode when doing the "initial" checkout. "Initial" means that the
index is empty before the checkout. This was not handled correctly in
JGit and is fixed in this commit. Also see
https://github.com/git/git/blob/master/Documentation/git-read-tree.txt#L181
Change-Id: I9b9d1bd9ebf349cfca420c891c7b099a18d07ba4