Handle migrated versions metadata table auto-update

[goetas]

Q	A
Type	feature
BC Break	no
Fixed issues	#788 #828

Summary

This PR:

• adds a command migrations:sync-metadata-storage that ensure the table scheme doctrine_migrations is always up to date
• auto-migrates the v2 table structure to the v3 table structure
• each command before starting checks if the metadata table is up to date

The Allow phpunit 7.5 commit should be removed when #879 will be merged

[goetas]

@jwage From the git history, in 2.x you have implemented the https://github.com/doctrine/migrations/tree/2.2.x/lib/Doctrine/Migrations/Tracking feature, that was supposed to do something similar as this PR. Do you have time to review this please?

[greg0ire]

Prevent accidental merge, dismiss when second commit is removed

[greg0ire]

I think something went wrong with your last push, can you please check? None of my comments are addressed now…

[goetas]

@greg0ire my bad I forgot to pull the changes done via github UI.

• I have addressed your suggestions again.
• I have also removed the temporary commit
• i have improved the condition in Handle migrated versions metadata table auto-update  #878 (comment) by extracting it in a private method, now is much more clear the propose of that if condition

[goetas]

Since this feature is quite critical, can somebody else review/test it please?

[alcaeus]

@goetas I don't have any projects using migrations, and other people might be wondering this too: what would be the best way to test this?

[goetas]

The best way to test this is to have a project using migrations 2.x, try the upgrade process to 3.x as described in https://github.com/doctrine/migrations/blob/master/UPGRADE.md, and share the results.