Allow more fine grained controls in diff

[samuelstjean]

Seems like the git diff command is hardcoded in the source file and also flushes out the git config options if I read it correctly. As everything is also sandboxed, we use a regular git diff, without any bells or whistle the user might have installed to pimp the command. It would be nice to have the option to pass additional arguments, like say --word-diff, which would make one life much easier to quickly see when the only change in a package is only a version bump as we could highlight only the small changes instead of the whole line.

This would also make it more obvious if the upstream source changes by say typosquatting the url with a new maintainer instead of checking again the whole line as git diff would tell me.