Add option "ignore white spaces" in diff views

Diff views are:

  • commits
  • MR
  • compares
  • may be blames?

And currently (8.4) diff views can get clunky, with useless white spaces added / removed.
Need to have option to ignore them.
I propose to have checkbox in UI, something like this:
WhiteSpaces

I see, that ChangeLog says, that such functionality is added already in 8.2.0: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG#L304

Here is MR for that: https://gitlab.com/gitlab-org/gitlab-ce/commit/3d0efa8e0a359c84485a0fd7a3317745bf5648b8

But it doesn't work in 8.4.2. Not sure, if it is regression, or it never worked.

Here is related issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/5951 Blame with option to ignore whitespace changes (-w)