This is the code that takes a normal file and adds it to a TarWriter.
We extract it so that we can share it with Tar().
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Upstream-commit: 5b77e51e0a15eddefcb40380673df8c0c24f95d1
Component: engine