Show commits from source project. Be consistent with pipeline

## What does this MR do?

Show commits from source project instead of target project.

## Why was this MR needed?

To be consistent.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [x] Added for this feature/bug

## What are the relevant issue numbers?

Closes #3596

See merge request !6658