When changing code it maybe required to place and IF around it or change it's scope in any other way. If it happens that with scope developer also changed something in that code, then it's barely visible that way.

I propose to add "Ignore Whitespaces" option to per file "View Options" menu:

which will allow to see changes in current file ignoring all whitespace changes (the simplest case) or ignoring only leading/trailing whitespace changes (harder to do, but has it's uses cases as well).

Currently the GitHub supports secret "?w=1" in diffs to show diff ignoring whitespaces and Atlassian FishEye also has similar options.

Here is how diff looks in Phabricator (honoring whitespaces):

And here is how it would look in Araxis Merge (diff tool I'm using to solve this situation currently) with whitespaces ignored: