Comment on file blobs

Problem to solve

Currently I cannot comment on the latest blob of a file. Instead I have to enable blame mode, navigate to the commit and comment on the commit's diff.

Further details

This is mostly a minor nuisance as long as I can actually view and comment on the diff. It however becomes a major issue when that diff is too large to display (and comment on, see gitlab-ce#30061), because in that case I basically have no way of leaving review comments. The goal of this ticket is to have a way to comment on large diffs.

Proposal

Either provide a way to comment on file blobs or fix the issue in gitlab-ce#30061 for arbitrarily large diffs, so that all commits / merge requests are effectively reviewable. I would say that fixing gitlab-ce#30061 would reduce the impact of this feature proposal to basically zero.

What does success look like, and how can we measure that?

The merge request where I am experiencing an issue with this is unfortunately privately hosted and inaccessible to you, but any merge request adding a new 5000-line file (with a not-too-short line length, the file should exceed 1 MB I believe) should reproduce the issue. Success would be the ability to comment in any way on lines in this file that were included in the commit that introduced the file.

Links / references

gitlab-ce#30061: Unable to view diff for large file