Fix diff changes empty state

Closes #48635

See merge request gitlab-org/gitlab-ce!23767

Add List-Id to notification emails

Closes #53493

See merge request gitlab-org/gitlab-ce!22817

IE11: Fix sprite icon rendering

Closes #52774

See merge request gitlab-org/gitlab-ce!23773

Restore Object Pools when restoring an object pool

Closes gitaly#1355

See merge request gitlab-org/gitlab-ce!23682

The empty state now only gets shown when no files exist in the branch.
If the user is reviewing 2 versions with no files, we don't show the state.

Refactors the diff app spec to use Vue test utils.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/48635

Re-define default only except policy

Closes #55099

See merge request gitlab-org/gitlab-ce!23765

Update environments breadcrumb

Closes #48048

See merge request gitlab-org/gitlab-ce!23751

Fixed notes not being applied to diff lines

Closes #55245 and #55248

See merge request gitlab-org/gitlab-ce!23778

Fix mr_widget_icon responsive alignment

See merge request gitlab-org/gitlab-ce!23781

Pool repositories are persisted in the database, and when the DB is
restored, the data need to be restored on disk. This is done by
resetting the state machine and rescheduling the object pool creation.

This is not an exact replica of the state like at the time of the
creation of the backup. However, the data is consistent again.

Dumping isn't required as internally GitLab uses git bundles which
bundle all refs and include all objects in the bundle that they require,
reduplicating as more repositories get backed up. This does require more
data to be stored.

Fixes https://gitlab.com/gitlab-org/gitaly/issues/1355

Nurtch link

See merge request gitlab-org/gitlab-ce!23668

Add CSS helper classes for left and right padding

See merge request gitlab-org/gitlab-ce!23760

Document how to run rspec tests

See merge request gitlab-org/gitlab-ce!23780

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55248, https://gitlab.com/gitlab-org/gitlab-ce/issues/55245

Resolve various database deprecation warnings

See merge request gitlab-org/gitlab-ce!23772

Refactor Project#create_or_update_import_data

See merge request gitlab-org/gitlab-ce!23701

Do not save user preferences on read-only mode

Closes #55024

See merge request gitlab-org/gitlab-ce!23698

The use of `table_exists?` in the opclasses support initializer triggers
a deprecation warning. Using `data_source_exists?` removes this
deprecation.

Extending from ActiveRecord::Migration is deprecated, but was still used
in a bunch of places.

Ref
https://docs.gitlab.com/ee/development/documentation/styleguide.html#lin
ks

Add basic implementation of CI/CD bridge job

See merge request gitlab-org/gitlab-ce!23730

Wait for push before trying to create a new MR

See merge request gitlab-org/gitlab-ce!23745

Fix creation query for pools repository

See merge request gitlab-org/gitlab-ce!23729

Send a notification email on mirror update errors

Closes #54650

See merge request gitlab-org/gitlab-ce!23595

Update automatic merging documentation

See merge request gitlab-org/gitlab-ce!23689