If a user makes a mistake, he can not go back and modify the bugtracker type indicated. To solve this problem, we could allow the end-user to change the type later in the bugtracker's +edit page.
To minimize this problem, we could infer the bugtrackertype automatically (by, for instance, trying to load bug #1 in the tracker and seeing if a 404 page is returned)
We need to be a bit careful with this because of one case: when a project changes bugtrackers. In that situation, depending on whether the project is migrating their bugs, and depending on whether the former bugtracker is still up, we may end up with some linkrot. It should be clear in the interface that you should not just go in and change the type if your project is changing bugtrackers. Or something like that. :-)
