Feature: diff between 2 commits

[Camts]

Hello,
The only feature Guitar has not and that I really need to use as main git tool (currently smartgit) is diff between 2 commits.
Use cases I have very often:

• compare branch with master to have nice diff so as to valid a merge request
• compare branch in origin and local branch after a git rebase (with or without --interactive) to verify

We could click on a commit, then control+click on another, then both commits would be selected and file list panel would show git diff --raw result. Of course, all buttons (Select all, Stage, Unstage and Commit) in this panel would be disabled.