[ticket/12561] Add "after" check to schema_generator for columns_add
* PayBas/ticket/12561:
[ticket/12561] Reworked tests by nickvergessen
[ticket/12561] Added tests for "after last", "after missing" and "empty"
[ticket/12561] Add check to see if "after" column actually exists
[ticket/12561] Added test for "after"
[ticket/12561] Add "after" check to schema_generator for columns_add
The migration helper currently drops any keys with schema changes that have
the data_depth 1. This change will correctly assign the keys to the steps
array without dropping the keys that might contain important info like the
actual table that should be created.
PHPBB3-12170
Allows you to check if the migration is effectively installed
(entirely optionall)
This function is intended to help moving to migrations from a
previous database updater, where some migrations may have been
installed already even though they are not yet listed in the
migrations table.
PHPBB3-9737
This is required so that when migrations are reverted we can check through
all installed migrations and make sure that all dependencies are handled
properly and so that we are only required to load the migrations files
that could be dependent on the ones installed.
I believe in normal proper use the old way might have worked, but in case
something happens and an unrelated migration file is installed, but cannot
be loaded, this makes sure we do not stop everything unless we absolutely
must (one of those files is dependent on something we want to revert).
PHPBB3-9737
This is used when a long-running process is needed during an update. For
example, iterating over all posts and applying some transformation. This
allows the process to be broken apart into multiple shorter steps to prevent
hitting the time limit.
PHPBB3-9737
Returning the set of schema changes allows potentially aggregating to generate
the overall install schema automatically from a set of migrations
PHPBB3-9737
