Upgrade - Bump minimum upgradable version to 4.6.12

[colemanw]

Overview

Removes old upgrade code, requires at least version 4.6.12 to upgrade to the latest version of CiviCRM in a single step (upgrading from older versions is still possible by breaking it into smaller steps, e.g. 4.4 -> 4.6, then 4.6 -> latest.

Before

Minimum upgradable version = 4.5

After

Minimum upgradable version = 4.6

Comments

I know it's been less than a year since the last bump, but 4.5 was not an LTS release so hasn't been supported for a very long time.

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[totten]

I think the test failure indicates that we should bump up https://github.com/civicrm/civicrm-buildkit/blob/f4901d24508cf335584f5aaa711584a632262497/bin/civi-test-run#L348

Relatedly, we really should add some more snapshots to https://github.com/civicrm/civicrm-upgrade-test/tree/master/databases... maybe snapshots for a few 5.x ESRs...

[totten]

civicrm/civicrm-buildkit#659 should make test system ignore the older snapshots (and start testing some newer snapshots).

[totten]

jenkins, test this please

[colemanw]

Thanks @totten this is passing now.

[totten]

Cool. Merging.