Allow replacing whitespace with glyphs in code views

Description

In various parts of our code base we use different kinds of whitespace for indentation - sometimes tabs (various DSLs we have to use), sometimes spaces (the normal code).

During code reviews we would like to see whether the developer used tabs or spaces in the file - as of now, we have to verify that manually (by selecting the whitespace manually with the mouse, for each line) or rely on tools like checkstyle or custom checkers to include proper checks during CI processing. These tools often integrate quite poorly with the review process.

Replacing whitespace (tabs, spaces) with replacement glyphs (tab arrows, space dots or similar) would make that much easier. Since it could annoy some, it should be optional rather than mandatory.

Proposal

Allow optionally highlighting the kind of whitespace being used in code views (especially diffs) by showing glyphs (arrows, dots) rather than whitespace.