$DIB_OFFLINE and $DIB_DEBIAN_USE_DEBOOTSTRAP_CACHE are redundant

[Augustina Ragwitz]

The environment variables $DIB_OFFLINE and $DIB_DEBIAN_USE_DEBOOTSTRAP_CACHE are documented as both indicating that debootstrap should use a local tarball. I did some digging and found these variables only used in one line in /elements/debootstrap/root.d/08-debootstrap, specifically " if [ -n "$DIB_OFFLINE" -o -n "${DIB_DEBIAN_USE_DEBOOTSTRAP_CACHE:-}" ] && [ -f $DEBOOTSTRAP_TARBALL ] ; then". Seems like one of these should be removed, unless something else is using it?

[xion (xionchen)]

Those variables are not redundant,they hava different effective ranges.
However,some people may be confused about this and reported a bug.
So,this difference should be writen in the REAME file.

https://review.openstack.org/#/c/345935/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/345935
Committed: https://git.openstack.org/cgit/openstack/diskimage-builder/commit/?id=ff234b65ea2415708581089ef2061e26ee1fa6da
Submitter: Jenkins
Branch: master

commit ff234b65ea2415708581089ef2061e26ee1fa6da
Author: Xiang Chen <email address hidden>
Date: Mon Jul 25 10:15:42 2016 +0800

    Explain difference between two envvars

    Explain difference between 'DIB_OFFLINE' and
     'DIB_DEBIAN_USE_DEBOOTSTRAP_CACHE'

    Those variables are not redundant,they hava different effective ranges.
    However,some people may be confused about this and reported a bug.
    So,this difference should be writen in the README file.

    Closes-Bug: #1506275

    Change-Id: Ie5316de41d129bf98781708954f09ef0b2592b53

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/diskimage-builder 1.19.0 release.