Interact on existing branch

Hi Lucas,

The first commit is only a workaround of https://github.com/lmr/inspektor/issues/2

The second commit removes the master autoupdate before check_patch. I hate this autoupdate as sometimes I want to check the patch according to older version (eg. when the patch is not acceptable on the latest master). Well my origin is outdated, so it fails anyway so feel free to skip this one.

Last two patches simplifies the workflow when you inspect pull request you already inspected before. My personal favorite is OldBase as then I can simply call `git diff github-xx_x` and see what changed in this pull request (when your master is different from previous inspect and you just rename it, git diff is useless as many other patches were already applied).

Please feel free to smash it down with hammer, it's not well written. I just wanted to have something useful to talk about these automatic scenarios (I currently have to do manually).

Kind regards,
Lukáš