[Sub Issue] Project Commit & Snippets comments

Resources

FE @iamphill

Meta issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/13680

Proposal

Project commits and snippets comments should follow the same structure we have set up for merge requests. Side by side view should be full width, while the rest of the content is contained to the limited layout width. Inline view should have a max width set to the limited layout width.

Example:

---

Old Proposal

new max-width: 790px

Old

New Design:

cc: @tauriedavis @hazelyang @cperessini

if good, I'll assign front end label