bitbake/fetch2/git: Switch to completely use bare clones
We no longer need index/workdir support in the mirror tree and it causes all
kind of reference naming problems.Simplifying the code to remove this and use
just bare clones addresses this problem.
We increase the "version" number on the mirror tarballs to reflect the change
and ensure older mirror tarballs are not used as they would break.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
