manage comments

[b4mboo]

Enable the user to display existing comments and add new ones.

[b4mboo]

I edited a couple of minor things and renamed the command to simply 'discussion', as I thought it was too long otherwise. I also added output for additional commits. However, this is not complete yet, as I think it would be nice to have all commit messages in there (including the initial one, which is missing at the moment). At some point I'd like to merge this command into 'show', such that the user has all relevant information at once.

The only thing missing to close this issue is a command 'comment' that takes the ID and a string to create a new comment. I was thinking of sth. like this:
git review comment 42 -m 'new comment'
or a prompt if the -m is missing ("Please enter your comment:").

[b4mboo]

OK, I merged discussion into 'show', since I don't think there are real use cases for having it a separate command. Also, 'show' really gives a very good overview about what's happening.

[b4mboo]

I added the command 'approve' that basically just adds a comment. Eventually, some refactoring will help to close this issue here, too, by just using the already present code. Assigning myself to the task.