This method was moved to ::Git but it is not cached there which causes performance problems

When querying the deployments of an environment the query Rails produces
will be along the lines of the following:

    SELECT *
    FROM deployments
    WHERE environment_id = X

For queries such as this (or queries that use this as their base and add
more conditions) there is no meaningful index that can be used as long
as deployments.project_id is not part of a WHERE clause.

To work around this we change that "has_many :deployments" relation to
always add a "WHERE project_id = X" condition. This means that queries
filtering deployments can make better use of the existing indexes. For
example, when filtering by deployments.iid this will result in the
following query:

    SELECT *
    FROM deployments
    WHERE environment_id = X
    AND project_id = Y
    AND iid = Z

This means PostgreSQL can use the existing index on
(project_id, environment_id, iid) instead of having to use a different
index (or none at all) and having to scan over a large amount of data.

Query plan wise this means that instead of this query and plan:

    EXPLAIN (BUFFERS, ANALYZE)
    SELECT deployments.*
    FROM deployments
    WHERE deployments.environment_id = 5
    AND deployments.iid = 225;

    Index Scan using index_deployments_on_project_id_and_iid on deployments  (cost=0.42..14465.75 rows=1 width=117) (actual time=6.394..38.048 rows=1 loops=1)
      Index Cond: (iid = 225)
      Filter: (environment_id = 5)
      Rows Removed by Filter: 839
      Buffers: shared hit=4534
    Planning time: 0.076 ms
    Execution time: 38.073 ms

We produce the following query and plan:

    EXPLAIN (BUFFERS, ANALYZE)
    SELECT deployments.*
    FROM deployments
    WHERE deployments.environment_id = 5
    AND deployments.iid = 225
    AND deployments.project_id = 1292351;

    Index Scan using index_deployments_on_project_id_and_iid on deployments  (cost=0.42..4.45 rows=1 width=117) (actual time=0.018..0.018 rows=1 loops=1)
      Index Cond: ((project_id = 1292351) AND (iid = 225))
      Filter: (environment_id = 5)
      Buffers: shared hit=4
    Planning time: 0.088 ms
    Execution time: 0.039 ms

On GitLab.com these changes result in a (roughly) 11x improvement in SQL
timings for the CI environment status endpoint.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/36877

Before this fix, I don't know if those emails would work
having newlines in them.

added a QueryRecorder for IssuesController#index.json

This reverts merge request !14148

This enables skipping a lesser housekeeping task
(incremental or full repack) by consistently
scheduling a higher task (respectively full repack or gc)
with the same period.
Cf. #34981

Revert "Merge branch '35012-navigation-add-option-to-change-navigation-color-palette' into 'master'"

This reverts merge request !13619

Do not use `location.pathname` when accessing environments folders

See merge request !2147

Whenever you push to a branch GitLab will show a button to create a
merge request (should one not exist already). The underlying code to
display this data was quite inefficient. For example, it involved
multiple slow queries just to figure out what the most recent push event
was.

This commit changes the way this data is retrieved so it's much faster.
This is achieved by caching the ID of the last push event on every push,
which is then retrieved when loading certain pages. Database queries are
only executed if necessary and the cached data is removed automatically
once a merge request has been created, or 2 hours after being stored.

A trade-off of this approach is that we _only_ track the last event.
Previously if you were to push to branch A and B then create a merge
request for branch B we'd still show the widget for branch A. As of this
commit this is no longer the case, instead we will only show the widget
for the branch you pushed to most recently. Once a merge request exists
the widget is no longer displayed. Alternative solutions are either too
complex and/or too slow, hence the decision was made to settle for this
trade-off.

Performance Impact
------------------

In the best case scenario (= a user didn't push anything for more than 2
hours) we perform a single Redis GET per page. Should there be cached
data we will run a single (and lightweight) SQL query to get the
event data from the database. If a merge request already exists we will
run an additional DEL to remove the cache key.

The difference in response timings can vary a bit per project. On
GitLab.com the 99th percentile of time spent in User#recent_push hovers
between 100 milliseconds and 1 second, while the mean hovers around 50
milliseconds. With the changes in this MR the expected time spent in
User#recent_push is expected to be reduced down to just a few
milliseconds.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/35990

…when needed

This finishes the procedure for migrating events from the old format
into the new format. Code no longer uses the old setup and the database
tables used during the migration process are swapped, with the old table
being dropped.

While the database migration can be reversed this will 1) take a lot of
time as data has to be coped around 2) won't restore data in the
"events.data" column as we have no way of restoring this.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/37241

also fix some code styling issues

 - only show in merge-requests
 - show as a little glyph

this will remove the need make N queries (per-note) at the
cost of having to mark notes with an attribute

this opens up the possibility for other special roles for notes