preversioning versions don't take pre-release tags into account

[Robert Collins]

In neutron's stable/kilo branch, top four commits and their pbr versions:
7260e0e Run radvd as root [tagged 2015.1.0rc3 ] => 2015.1.0.0rc3
d37e566 Don't resync on DHCP agent setup failure => 2015.1.0.dev1
9e11336 Merge "Restrict subnet create/update to avoid DHCP resync" into stable/kilo [tagged 2015.1.0rc2]=> 2015.1.0.0rc2

The middle version is wrong - it preceeds the rc versions.
(x.dev < x.rc1.dev < x.rc1 < x.rc2.dev < x.rc2 < x)

To reproduce in a neutron tree:
$ git reset --hard d37e566
HEAD is now at d37e566 Don't resync on DHCP agent setup failure
$ git describe
2015.1.0rc2-1-gd37e566
$ python setup.py egg_info
$ grep Version neutron.egg-info/PKG-INFO
Version: 2015.1.0.dev1

What we'd expect is 2015.1.0.0rc3.dev1 which will be generated if we remove version: from setup.cfg.

Preversioning is the culprit:
556 if distance == 0:
557 return last_semver
558 import pdb;pdb.set_trace()
559 -> if target_version is not None:
560 return target_version.to_dev(distance)
561 else:
562 return new_version.to_dev(distance)

A possible fix would be to compare target_version.to_dev(distance) with new_version.to_dev(distance), and take the higher.

I'm not sure that it won't fall out somewhere else, but its worth trying.

[Robert Collins (lifeless)]

(from 1206730)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/178852

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/178852
Committed: https://git.openstack.org/cgit/openstack-dev/pbr/commit/?id=a67e2c346c5193cf36e381694d8fddb0d826df6b
Submitter: Jenkins
Branch: master

commit a67e2c346c5193cf36e381694d8fddb0d826df6b
Author: Robert Collins <email address hidden>
Date: Thu Apr 30 09:47:22 2015 +1200

    Issue #1450210: Preversioning rc tag handling

    We were generating versions lower than the last tag when preversioning
    was in use and pre-release versions had been tagged.

    Also attempt to run the script without devstack.

    Change-Id: If984939003ae7c513ee76b52c6808db0c1766050
    Closes-Bug: #1450210