Squash merge request compare and commits compare into one page
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Dev: https://dev.gitlab.org/gitlab/gitlabhq/issues/1436
Right now we have 2 different pages for same functionality - comparing commits. We need to make one page from two.
Why?
- it uses different logic that cause different behaviour.
- it causes a lot of duplication in code
- it cause confusion from UI/UX perspective
cc/ @JobV @dzaporozhets @sytses
issue