Test diffs are too hard to visualize on CI

[steve-chavez]

Problem

When CI fails due to an error in the tests, they're hard to visualize:

• The raw logs have to be accessed.
• Then one has to CTRL +F "regression.diffs".

The feedback must be immediate or otherwise fixing tests is a chore, team members are not fixing them quickly. See an example here #994 (comment).

Solution

Provide a clean way to see the regression.diffs on CI, without having to access raw logs.

Notes

The CI logs contain a full dump of the bash scripts used, the successful output of tests, all of which is completely unnecessary. It should only contain errors.