Removing those weird setup in assign_change_commit_vars
fixed all the failures in the tests. I still cannot say
why but clearly we need to have better names. It's so
confusing right now. We should seriously stop fiddling
those instance variables.

This is seriously confusing but a target branch in merge request,
is actually the source branch for GitOperationService, which is
the base branch. The source branch in a merge request, is the
target branch for GitOperationService, which is where we want to
make commits.

Perhaps we should rename source branch in GitOperationService to
base branch, and target branch to committing branch.

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20571990

We merge repository checks inside it so we don't have to
check it on the call site, and we could also load the commit
for the caller. This greatly reduce code duplication.

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20572919

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20876648

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20601323

Feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20301332

* master: (1031 commits)
  Add changelog entry for renaming API param [ci skip]
  Add missing milestone parameter
  Refactor issues filter in API
  Fix project hooks params
  Gitlab::LDAP::Person uses LDAP attributes configuration
  Don't delete files from spec/fixtures
  Copy, don't move uploaded avatar files
  Minor improvements to changelog docs
  Rename logo, apply for Slack too
  Fix Gemfile.lock for the octokit update
  Fix cross-project references copy to include the project reference
  Add logo in public files
  Use stable icon for Mattermost integration
  rewrite the item.respond_to?(:x?) && item.x? to item.try(:x?)
  API: extern_uid is a string
  Increases pipeline graph drowdown width in order to prevent strange position on chrome on ubuntu
  Removed bottom padding from merge manually from CLI because of repositioning award emoji's
  Make haml_lint happy
  Improve spec
  Add feature tests for Cycle Analytics
  ...

Refactor issues filter in API

See merge request !8432

Add changelog entry for renaming API param

See merge request !8433

Fix project hooks params

Closes #26291

See merge request !8425

Gitlab::LDAP::Person uses LDAP attributes configuration

Closes #26290

See merge request !8418

Resolves overflow of dropdown text for long branch name

Closes #25580

See merge request !8118

Merge branch '25836-changing-from-version-in-diff-comparison-does-not-preserve-to-version' into 'master'

Resolve changing "from" version in diff comparison does not preserve "to" version

Closes #25836

See merge request !8328

We allow users to configure LDAP attribute preferences. For example,
email can be configured to use `mail`, `email` and `userPrincipalName`,
falling through to the next until a value is found. Prior to this
change, Gitlab::LDAP::Person did not honor this configuration. Now,
the class will honor `name` and `mail` configuration. It does not
handle `username`, or fallback to `first_name` + `last_name` in the
absence of `name`.

Resolve "Label autocomplete doesn't handle spaces after `~~`"

Closes #25964, #22058, and #23578

See merge request !8254

Disable award emoji button but display tooltip

Closes #26168

See merge request !8382

Removed bottom padding from merge manually from CLI because of repositioning award emoji's

See merge request !8398

Fixed regression of note-headline-light where it was always placed on 2 lines, e…

See merge request !8348

Use stable icon for Mattermost integration

See merge request !8252

Revert specific URL

See merge request !8321

Copy, don't move uploaded avatar files

Closes #26158

See merge request !8396

Fix cross-project references copy to include the project reference

Closes #25890

See merge request !8232

Remove bottom border from Issuable titles

See merge request !8278

[ci skip]

Fix Gemfile.lock for the octokit update

See merge request !8414

MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8158 updated
the octokit Gem but did not include all the changes for Gemfile.lock.

Also added relevant specs and refactored to_references in a bunch of places to be more consistent.