bug 1385405: Add ways for viewing submodule logs
bug 1385405: Add ways for viewing submodule logs

Create long alias submodule-compare-urls for opening the logs in
GitHub's compare view.

Add a command for seeing just the merge commits, suggested by
@safwanrahman

escattone/kuma,Elchi3/kuma,jwhitlock/kuma,mozilla/kuma,SphinxKnight/kuma,jwhitlock/kuma,jwhitlock/kuma,escattone/kuma,mozilla/kuma,Elchi3/kuma,jwhitlock/kuma,SphinxKnight/kuma,Elchi3/kuma,a2sheppy/kuma,SphinxKnight/kuma,SphinxKnight/kuma,mozilla/kuma,a2sheppy/kuma,Elchi3/kuma,a2sheppy/kuma,jwhitlock/kuma,mozilla/kuma,SphinxKnight/kuma,Elchi3/kuma,mozilla/kuma,a2sheppy/kuma,SphinxKnight/kuma,a2sheppy/kuma,escattone/kuma