It won't change anything after they are first invoke, so add method cache to avoid allocations and avoid GC.

Benchmarks:

```
Calculating -------------------------------------
project_guest_rules without method cache
                        79.352k i/100ms
project_guest_rules with method cache
                        93.634k i/100ms
-------------------------------------------------
project_guest_rules without method cache
                          2.865M (±32.5%) i/s -     11.982M
project_guest_rules with method cache
                          4.419M (± 7.4%) i/s -     22.004M

Comparison:
project_guest_rules with method cache:  4418908.0 i/s
project_guest_rules without method cache:  2864514.0 i/s - 1.54x slower

Calculating -------------------------------------
project_report_rules without method cache
                        53.126k i/100ms
project_report_rules with method cache
                        97.473k i/100ms
-------------------------------------------------
project_report_rules without method cache
                          1.093M (±36.5%) i/s -      4.675M
project_report_rules with method cache
                          4.420M (± 7.2%) i/s -     22.029M
Comparison:
project_report_rules with method cache:  4420054.3 i/s
project_report_rules without method cache:  1092509.6 i/s - 4.05x slower
```

https://gist.github.com/huacnlee/b04788ae6df42fe769e4

update guides for feature proposals on the issue tracker

see also #4038 

cc @sytses 

See merge request !2094

Fix Typo [mailinglist to mailing list]

Closes: #4078 

See merge request !2098

[ci skip]

Add upgrade guide for 8.2 to 8.3

Making sure we don't forget mentioning the need to upgrade Redis from
!1888. Added this in preparation for 8.3.

[ci skip]

See merge request !2085

[ci skip]

[ci skip]

[ci skip]

[ci skip]

Suppress warning about missing `.gitlab-ci.yml` if builds are disabled

When user disables GitLab Ci Service in project's settings then warning
about missing `.gitlab-ci.yml` file should be supressed. This a matter
of user experience as stated in #3761 (closes #3761).

cc @ayufan 

See merge request !2014

[ci skip]

Persist CI runners registration token

This MR adds feature of persisting CI runners registration token.
User will be able to generate and then reset (if necessary to revoke) this token.

This closes #3703 

cc @ayufan 

See merge request !2039

* master:
  Move CI admin builds and runners specs to correct directory
  Fix 500 when viewing specific runners on runners page
  Fix Ci::Project migration not migrating columns that cannot be NULL
  Fix MySQL migration of CI emails
  Minor fix in flow 'Merge when build succeeds'

Move CI admin builds and runners specs to correct directory [ci skip]

/cc @grzesiek 

See merge request !2095

Fix CI project migration and 500 on runners page



See merge request !2093

* master: (66 commits)
  Fix runners admin view
  Fix migrations
  Rename mention of gitlab-git-http-server to gitlab-workhorse
  Bump Redis requirement to 2.8 for Sidekiq 4 requirements
  Fix wording on runner setup page
  add details on how to change saml button label
  Fix tests
  Move awards back to gray panel and few improvements to sidebar
  Few UI improvements to new sidebar implementation
  Fix tests for new issuable sidebar
  Update changelog
  Implement new sidebar for merge request page
  Make edit link on issuable sidebar works
  Redesign issue page for new sidebar
  Move awards css to separate file
  Implement issuable sidebar partial
  Update CHANGELOG
  Clarify cache behavior
  Run builds from projects with enabled CI
  Use Gitlab::Git instead of Ci::Git
  ...

Conflicts:
	db/schema.rb

* master: (24 commits)
  Fix runners admin view
  Fix migrations
  Run builds from projects with enabled CI
  Use Gitlab::Git instead of Ci::Git
  Fix last specs
  Fix specs
  Fix after column rename
  Fix errors
  Update badge
  Finishing touches
  Fix triggers tests
  Rename columns and rename migrations
  Reimplement Trigger API
  Remove ci_ prefix from all ci related things
  Add runners token
  Migrate CI::Project to Project
  Fix indentation and BuildsEmailService
  Change default values
  Enhance migrate CI emails
  Fix issue tracker service
  ...

Conflicts:
	spec/features/commits_spec.rb

Minor fix in flow 'Merge when build succeeds'

When a user, which is not the merge user, want to removes the source branch
after the automatic merge this might fail because of checks in the
DeleteBranchService

/cc @DouweM 

See merge request !2070

Ci Project migrate

- This doesn't migrate: allow_git_fetch, coverage_regex, timeout. Since this are project configuration settings I would propose to migrate them to `.gitlab-ci.yml`.
- This requires offline migrations.
- It simplifies database models making all CI objects to be attached to: Project.
- It removes Ci::Project, but makes /ci/projects working by adding method: Project.find_by_ci_id for backward compatibility (badges, triggers).
- We should add default `timeout` to Application Settings.
- It misses specs.
- It is based on ci-services-migrate for now.
- It removes CI events.
- It removes administrator CI projects overview.
- It removes CI application settings.

In 8.4 or 8.5 we can remove redundant tables and columns.


See merge request !1987

Ci Services migrate



See merge request !1985

Ref #3827

This minimizes usage of instance variables in this spec, and changes
double quotation marks to single when string interpolation is not being
used.

When user disables GitLab Ci Service in project's settings then warning
about missing `.gitlab-ci.yml` file should be supressed. This a matter
of user experience as stated in #3761 (closes #3761).

Rename mention of gitlab-git-http-server to gitlab-workhorse

[ci skip]

Closes https://github.com/gitlabhq/gitlabhq/issues/9904

See merge request !2092

[ci skip]

Closes https://github.com/gitlabhq/gitlabhq/issues/9904

Fix wording on "runners" page

An attempt to be a bit more specific and clear on the "runners" page.

[ci skip]

See merge request !2066

Bump Redis requirement to 2.8 for Sidekiq 4

GitLab Omnibus already uses Redis 2.8. There is also a plan to upgrade to Sidekiq 4, which needs Redis 2.8.

Closes #3649

See merge request !1888