Summary: Ref T13249. - When a line has only increased in indent depth, don't red-fill highlight the left side of the diff. Since reading a diff //mostly// involves focusing on the right side, indent depth changes are generally visible enough without this extra hint. The extra hint can become distracting in cases where there is a large block of indent depth changes. - Move the markers slightly to the left, to align them with the gutter. - Make them slightly opaque so they're a little less prominent. Test Plan: See screenshots. Reviewers: amckinley Reviewed By: amckinley Maniphest Tasks: T13249 Differential Revision: https://secure.phabricator.com/D20251