WIP - trying to replicate UTF-8 error

fix spec

fixing encoding issue and another spec, to do with MR diffs

fix issue and spec failure

Add changelog and bumped up I/E version

fix spec based on feedback - omitted target project

This reverts commit 530f5158.

See !4892.
Signed-off-by: NRémy Coutable <remy@rymai.me>

added changelog

This reverts commit 9ca633eb, reversing
changes made to fb229bbf.

1. Fix typos, minor styling errors.

2. Use single quotes rather than double quotes in `user_access_spec`.

3. Test formatting.

1. Don't use case statements for dispatch anymore. This leads to a lot
   of duplication, and makes the logic harder to follow.

2. Remove duplicated logic.

    - For example, the `can_push_to_branch?` exists, but we also have a
      different way of checking the same condition within `change_access_check`.

    - This kind of duplication is removed, and the `can_push_to_branch?`
      method is used in both places.

3. Move checks returning true/false to `UserAccess`.

    - All public methods in `GitAccess` now return an instance of
      `GitAccessStatus`. Previously, some methods would return
      true/false as well, which was confusing.

    - It makes sense for these kinds of checks to be at the level of a
      user, so the `UserAccess` class was repurposed for this. The prior
      `UserAccess.allowed?` classmethod is converted into an instance
      method.

    - All external uses of these checks have been migrated to use the
      `UserAccess` class

4. Move the "change_access_check" into a separate class.

    - Create the `GitAccess::ChangeAccessCheck` class to run these
      checks, which are quite substantial.

    - `ChangeAccessCheck` returns an instance of `GitAccessStatus` as
      well.

5. Break out the boolean logic in `ChangeAccessCheck` into `if/else`
   chains - this seems more readable.

6. I can understand that this might look like overkill for !4892, but I
   think this is a good opportunity to clean it up.

    - http://martinfowler.com/bliki/OpportunisticRefactoring.html

1. When a merge request is being merged, save the merge commit SHA in
   the `in_progress_merge_commit_sha` database column.

2. The `pre-receive` hook looks for any locked (in progress) merge
   request with `in_progress_merge_commit_sha` matching the `newrev` it
   is passed.

3. If it finds a matching MR, the merge is legitimate.

4. Update `git_access_spec` to test the behaviour we added here. Also
   refactored this spec a bit to make it easier to add more contexts / conditions.

- Cherry-picked from `mvestergaard:branch-protection-dev-merge`
- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4220

squashed - refactor to cope with sub sub N relations probably using the sub_relations method recursively.

Rename ENV['PROTOCOL'] to ENV['GL_PROTOCOL'] to conform to what GitLab Shell expects and make the `protocol` param in `GitAccess` mandatory.

Note: This feature was developed independently on master while this was
in review. I've removed the conflicting bits and left the relevant
additions, mainly a test for `Gitlab::Git::Hook`. The original commit
message follows:

1. `gitlab-shell` outputs errors to `stderr`, but we weren't using this
   information, prior to this commit. Now we capture the `stderr`, and
   display it in the flash message when branch creation fails.

2. This can be used to display better errors for other git operation
   failures with small tweaks.

3. The return value of `Gitlab::Git::Hook#trigger` is changed from a
   simple `true`/`false` to a tuple of `[status, errors]`. All usages
   and tests have been updated to reflect this change.

4. This is only relevant to branch creation _from the Web UI_, since SSH
   and HTTP pushes access `gitlab-shell` either directly or through
   `gitlab-workhorse`.

5. A few minor changes need to be made on the `gitlab-shell` end. Right
   now, the `stderr` message it outputs is prefixed by "GitLab: ", which
   shows up in our flash message. This is better removed.