Add option to directly diff changes between hashes of submodules in a new tab

[themilkman]

Problem description

I often use submodules and need to see the changes of it. Currently, I always have to copy to old hash, open the submodule in a new tab, search the commit hash and shift-select the current to show the changes.

This was extracted from my comment #126

Preferred solution

Having an option on the ... button on near the "commit hash of submodule change" view (you know, where there is a text <submodule updated 223fa54f7f2ab021f3d1fee216087e6d396006a5 → 4246b7a02d2a17d66035f502756fb3eca684a68c>) which opens the submodule in a new tab (if not already opened) and directly selects the two commit hashes to see the diff should be easy to implement but very helpful addition imho.

[themilkman]

As an addition it might be nice to be able to click on one of the two the revision hashes and jump directly to the corresponding commit.