Get merge_requests patch 500

Request url is : http://url/group/repo/merge_requests/171.patch

Log is: Processing by Projects::MergeRequestsController#show as PATCH Parameters: {"namespace_id"=>"group", "project_id"=>"repo", "id"=>"171"} Completed 500 Internal Server Error in 552ms (ActiveRecord: 66.4ms) Rugged::InvalidError (Commit d87401bf08144546468cbf1db4da5b1c31720f1c is a merge commit): app/models/repository.rb:165:in method_missing' app/models/merge_request.rb:271:into_patch' app/controllers/projects/merge_requests_controller.rb:53:in block (2 levels) in show' app/controllers/projects/merge_requests_controller.rb:49:inshow'

This seems to be a recurrence of what 5f3a7587 was trying to solve: if the diff between two SHA elements contains a merge commit, Rugged's to_mbox method throws an Exception since Rugged doesn't support that at the moment.

It seems like there are two ways to solve this issue:

1. Add support for merge commits in libgit2 and rugged
2. Use the git command-line to generate the e-mail patch

Thanks @stanhu.Will it be fixed in new version? My version is 8.0.3 (omnibus).

It also has problem in 8.5.1

Yes, I don't think anyone has worked on this yet. Fixing libgit2/rugged would be the ideal approach, but this may be a bit tricky. Nonetheless, this seems like an important issue to fix.

/cc: @DouweM

Added repository label

Added ~12980 label

Milestone changed to 8.8

@stanhu It would be nice to fix, but I don't think it's super urgent.

mentioned in commit gitlab_git@f86bdce1

mentioned in merge request gitlab_git!74 (merged)

Actually, the fix is really simple! It appears that git format-patch also ignores merge commits, so that's all we have to do. Submitted via gitlab_git!74 (merged).

Status changed to closed by commit gitlab_git@f86bdce1

@stanhu @DouweM When will this fix be available?

@wbshen It already shipped in GitLab 8.6. Please let us know if it works for you.

Milestone changed to 8.6

@stanhu It works, Thanks!