"Download as diff" is broken for an MR

Look at this: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1186/diffs

A neat one-line changeset. Now try "Download as diff" (same as clicking https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1186.diff). After some quite a churn, this produces a diff over 9000 lines long that wants to undo a lot of later changes to the master.

Looks like a symmetric difference ... operator was used somewhere instead of .. when calling git diff, but I am not qualified to find where the breakage occurs, sorry.

Good catch. You are right; the code for symmetric difference operator is here. There was some work in gitlab_git!41 (merged) to support the double-dot operator, but perhaps this is a good reminder to renew that effort.

/cc: @ben.boeckel

@stanhu, @ben.boeckel: If I understand what repo.diff is, then it should be just

repo.diff(base, head, actual_options, *paths)

without the common commit. Just like diff base head. Am I missing something?

Right, that's all that's needed in this case. I think there needs to be an option in the controller and gitlab_git to toggle this on for the diff generation case.

Added ~12980 label

Added reproduced on GitLab.com label

Still in 8.6RC

mentioned in issue #14680 (closed)

Related to #14680 (closed)

Reassigned to @brodock

Milestone changed to 8.7

mentioned in merge request !3450 (merged)

Status changed to closed by merge request !3450 (merged)

mentioned in commit 3d484861

mentioned in commit 0a3f5adf

Mentioned in commit maxraab/gitlab-ce@0a3f5adf