8.1 cannot create MR 'merge_request_diff is nil'

Completed 500 Internal Server Error in 3320ms (ActiveRecord: 82.7ms)

ActionView::Template::Error (MergeRequest#commits delegated to merge_request_diff.commits, but merge_request_diff is nil: #<MergeRequest id: nil, target_branch: "master", source_branch: "git-archive-improvements", source_project_id: 13083, author_id: nil, assignee_id: nil, title: "Git archive improvements", created_at: nil, updated_at: nil, milestone_id: nil, state: "opened", merge_status: "unchecked", target_project_id: 13083, iid: nil, description: nil, position: 0, locked_at: nil, updated_by_id: nil, merge_error: nil>):
    15: 
    16: .files
    17:   - diff_files.each_with_index do |diff_file, index|
    18:     - diff_commit = commit_for_diff(diff_file.diff)
    19:     - blob = project.repository.blob_for_diff(diff_commit, diff_file.diff)
    20:     - next unless blob
    21: 
  app/models/merge_request.rb:45:in `rescue in commits'

mentioned in issue #3078 (closed)

@vsizov Can you check this?

@jacobvosmaer Was this just a random error that showed up in the logs? Not sure how to reproduce.

FWIW, my instance is also facing this "issue".

Old Gitlab installation from sources, no issue when running system checks.

System information
System:		Debian 7.9
Current User:	git
Using RVM:	no
Ruby Version:	2.1.5p273
Gem Version:	2.4.8
Bundler Version:1.10.6
Rake Version:	10.4.2
Sidekiq Version:3.3.0

GitLab information
Version:	8.1.0.pre
Revision:	6629163
Directory:	/home/git/gitlab
DB Adapter:	mysql2
Using LDAP:	no
Using Omniauth:	no

GitLab Shell
Version:	2.6.5
Repositories:	/home/git/repositories/
Hooks:		/home/git/gitlab-shell/hooks/
Git:		/usr/bin/git
Checking GitLab Shell ...

GitLab Shell version >= 2.6.5 ? ... OK (2.6.5)
Repo base directory exists? ... yes
Repo base directory is a symlink? ... no
Repo base owned by git:git? ... yes
Repo base access is drwxrws---? ... yes

Happy to give an hand to help find the root cause.

@rspeicher this reproduces the error:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/new?utf8=%E2%9C%93&merge_request%5Bsource_project_id%5D=13083&merge_request%5Bsource_branch%5D=git-archive-improvements&merge_request%5Btarget_project_id%5D=13083&merge_request%5Btarget_branch%5D=reproduce-500-for-3092

Reassigned to @DouweM

mentioned in merge request !1647 (merged)

Status changed to closed by commit f16bfa40

Thanks @DouweM

mentioned in commit 44d35a82

mentioned in commit f16bfa40

mentioned in issue #3207 (closed)

Any idea when this will be included in a release?

@iheart2code 8.1.2 will be out shortly.

@iheart2code @rspeicher That fix is already in 8.1.0GA. There is a similar issue with the same symptoms but a different root cause in #3207 (closed).

@DouweM @dzaporozhets could we get someone to look into #3207 (closed)? Similar issue.

@iheart2code I think @DouweM is looking into it

mentioned in merge request !14785