First, transitions between can_be_merged & cannot_be_merged are removed,
as they are currently blocked in `check_if_can_be_merged`.
`can_be_merge` always returns to `unchecked` first,
before it can transition to `cannot_be_merged` (and vice versa).

We want to avoid repeated notification triggered by repeated transition
between `cannot_be_merged` & `unchecked`.

So we added `cannot_be_merged_recheck` state, similar to `unchecked`,
but as a mean to remember it’s from cannot_be_merged.

See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18042/#note_65945407

Since `unchecked` and `cannot_be_merged_recheck` both mean
“we are in the middle of checking if it is mergeable”,
quite often we need to see if merge_status is in either one of them,
so `check_state?` is added to achieve this.

CE upstream - 2018-05-09 18:24 UTC

Closes gitlab-development-kit#348

See merge request gitlab-org/gitlab-ee!5642

[CE Port] Replace the `project/deploy_keys.feature` spinach test with an rspec analog

See merge request gitlab-org/gitlab-ee!5626

Move include SafeMirrorParams to EE module

See merge request gitlab-org/gitlab-ee!5631

Merge branch '5957-geo-secondary-can-t-log-failed-sign-in-attempts-due-to-read-only-db' into 'master'

Resolve "Geo: Secondary can't log failed sign-in attempts due to read-only DB"

Closes #5957

See merge request gitlab-org/gitlab-ee!5643

Epics - include ::Issuable, not EE::Issuable

See merge request gitlab-org/gitlab-ee!5644

# Conflicts:
#	db/schema.rb

[ci skip]

refactor "deploy_keys" to use axios

See merge request gitlab-org/gitlab-ce!18792

Fix project mirror data schema

See merge request gitlab-org/gitlab-ce!18811

Removed the d3_rails gem

See merge request gitlab-org/gitlab-ce!18860

# Conflicts:
#   db/schema.rb

Update documentation to use inclusive language, gender neutral name and pronoun.

See merge request gitlab-org/gitlab-ce!18858

Resolve "Incorrect documentation for .gitlab-ci.yml cache:key default value"

Closes #45840

See merge request gitlab-org/gitlab-ce!18841

Update documentation to use inclusive language, gender neutral name and pronoun.

See merge request gitlab-org/gitlab-ee!5597

Docs: fix duplicate titles

Closes #46061

See merge request gitlab-org/gitlab-ce!18758

Docs: fix duplicate titles

See merge request gitlab-org/gitlab-ee!5581

Add missing pipeline build foreign key to the schema

See merge request gitlab-org/gitlab-ce!18846

Add tmp index to ci_builds to optimize stages migration

Closes #46179

See merge request gitlab-org/gitlab-ce!18844

Remove rugged call in blame controller

See merge request gitlab-org/gitlab-ce!18817

Resolve "Skip EE specific check for CE upstream branches"

Closes #5950

See merge request gitlab-org/gitlab-ee!5636

CE upstream - 2018-05-09 12:24 UTC

Closes gitlab-com/gitlab-docs#200

See merge request gitlab-org/gitlab-ee!5633

# Conflicts:
#   db/schema.rb

Docs: update docs style guidelines

Closes #46157 and #45321

See merge request gitlab-org/gitlab-ce!18819

Remove project_mirror_data created_at and updated_at columns

Closes gitlab-qa#237

See merge request gitlab-org/gitlab-ee!5629

Support 'active' setting on Runner Registration API endpoint

See merge request gitlab-org/gitlab-ce!18848

Resolve "Bump upath to 1.0.5"

Closes #46003 and gitlab-development-kit#348

See merge request gitlab-org/gitlab-ce!18852