image-buildinfo: treat staged changes as modified branch, too
When staging changes in a layer using git add, image-buildinfo
doesn't detect this as a modification, because of the way it
uses git diff.
Surely, merely staging, but not committing changes to git
should not result in image-buildhistory assuming that the
git repository hasn't been modified compared to the branch
HEAD, this state should be treated similarly to modifications
being unstaged.
We have to use both, git diff and git diff --cached to get the
desired result.
Signed-off-by: André Draszik <adraszik@tycoint.com> Reported-by: Lukasz Nowak <lnowak@tycoint.com> Reviewed-by: Lukasz Nowak <lnowak@tycoint.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
