Pull Request resolves # .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Work in progress (WiP): I have to complete the summary of changes and testing instructions.

Summary of Changes

This pull request (PR) removes the compat6 backwards compatibility (b/c) plugin for Joomla 6 for new installation and updates, makes necessary adjustments of b/c plugin checks for the new major version 7 and finalises the addition of the compat7 b/c plugin for Joomla 7 which was made with PR #47420 but was not complete.

In detail, following changes are made:

• The compat6 plugin is removed for new installations (files installation/sql/<db type>/base.sql).
  As PR #47420 has added the new compat7 pugin with the same ordering 1 as the old one, this removal here does not require a change of the ordering values of other plugins of the same type.
• All files of the compat6 plugin are removed from sources, except of the legacy classes in the plugins/behaviour/compat6/classes folder and subfolders. These are moved to the new compat7 plugin as that was added with PR #47420 with the corresponding configuration option legacy_classes.
  This gives maintainers the time to decide for each class if it can be removed in 7 or not.
• The compat6 plugin is removed from the ExtensionsHelper (file libraries/src/Extension/ExtensionHelper.php), and the new compat7 plugin is added.
  The latter was forgotten with PR #47420 .
• Language files administrator/language/en-GB/plg_behaviour_compat7.ini and administrator/language/en-GB/plg_behaviour_compat7.sys.ini for the new compat7 plugins are added,
  This was forgotten with PR #47420 .
• System Information (file administrator/components/com_admin/src/Model/SysinfoModel.php) is changed to use the right plugin and not the old compat6. The change is made in a way so that it doesn't need a code change with every new major version, using Version::MAJOR_VERSION, similar to what was done with PRs #47807 and #47814 for the pre-update checks in 6.2-dev and meanwhile been merged up into 7.0-dev.
• The uninstallExtensions method in file administrator/components/com_admin/script.php is changed so that the compat6 plugin is removed when updating from 6.x to 7.0
• In file build/deleted_file_check.php the obsolete exclusions from 6.x are removed, and exclusions for the compat6 files are added so that they will not be reported to be added the deleted files list in script.php, which would cause them to be deleted on update before the uninstallExtensions method in file script.php is run.
• The exclusions in the phpstan-baseline.neon file are adapted for the right plugin.
• The exclusion from code style checks in file ruleset.xml are adapted for the right plugin.
• In system tests (file tests/System/integration/install/Installation.cy.js) the right plugin is disabled.

Testing Instructions

Code review.

Actual result BEFORE applying this Pull Request

Will be added soon.

Expected result AFTER applying this Pull Request

Will be added soon.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed