No "Rebase" option shown in MR for Reporter in FF-only project

Summary

When a Reporter opens a merge request in a project that requires fast-forward merges, and the branch to be merged isn't up to date (and the "Allow edits from maintainers" box isn't checked), the Developer willing to accept the merge request can't rebase it, but the Reporter isn't given enough indication that this needs to be done either.

Steps to reproduce

In a project with Merge method set to Fast-forward merge, have a user with Reporter status (able to create merge requests, not able to directly write to the project) create a new merge request from a branch that is behind the target branch.

The Reporter who created the merge request sees "Ready to be merged automatically. Ask someone with write access to this repository to merge this request." with no indication that the project settings disallow it from being merged as such, with no button available for rebasing it.

When the Developer with write access to the project reviews the merge request, willing to merge it, he sees "Fast-forward merge is not possible. Rebase the source branch onto master to allow this merge request to be merged.", but no Rebase button to actually do the rebase.

If the Reporter who created the merge request is given Developer level permission, he suddenly sees that his merge request in fact needs to be rebased (and is given a Rebase button to do this).

What is the current bug behavior?

The bug is that the merge request doesn't show that the branch needs to be rebased by the Reporter.

What is the expected correct behavior?

The Reporter should see the indication "Fast-forward merge is not possible. Rebase the source branch onto master to allow this merge request to be merged." with a Rebase button, even though the Reporter itself isn't allow to do the final merge into the target project.

Alternatively, the Developer should be able to do the rebase+merge operation within the destination project without touching the branch in Reporter's project.

Relevant logs and/or screenshots

Original view of MR by Reporter 1-contributor

Original view of MR by Developer 2-maintainer

View of MR by Reporter upgraded to Developer 3-contributor-maintainer

Results of GitLab environment info

Expand for output related to GitLab environment info 
# gitlab-rake gitlab:env:info
System information
System:		Ubuntu 16.04
Current User:	git
Using RVM:	no
Ruby Version:	2.3.7p456
Gem Version:	2.6.14
Bundler Version:1.13.7
Rake Version:	12.3.1
Redis Version:	3.2.11
Git Version:	2.16.4
Sidekiq Version:5.0.5
Go Version:	unknown

GitLab information
Version:	10.8.2
Revision:	d0a319c
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		<redacted>
HTTP Clone URL:	<redacted>
SSH Clone URL:	<redacted>
Using LDAP:	no
Using Omniauth:	no


GitLab Shell
Version:	7.1.2
Repository storage paths:
  • default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check 
# gitlab-rake gitlab:check SANITIZE=true
Checking GitLab Shell ...

GitLab Shell version >= 7.1.2 ? ... OK (7.1.2)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
2/5 ... ok
[.......]
14/739 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK


Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful


Checking GitLab Shell ... Finished


Checking Sidekiq ...


Running? ... yes
Number of Sidekiq processes ... 1


Checking Sidekiq ... Finished


Reply by email is disabled in config/gitlab.yml
Checking LDAP ...


LDAP is disabled in config/gitlab.yml


Checking LDAP ... Finished


Checking GitLab ...


Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
2/5 ... yes
[.......]
14/739 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.3.7)
Git version >= 2.9.5 ? ... yes (2.16.4)
Git user has default SSH configuration? ... yes
Active users: ... 15


Checking GitLab ... Finished