Ignore worktrees that aren't in one of the workspace folders

[alexr00]

Got an example from @digitarald where we end up doing everything 4 times because there are 3 worktrees in a repo.

[roblourens]

What is 'everything' and how do I verify this?

[alexr00]

@digitarald would you be able to verify this?

Otherwise, to verify:

• Create 3 worktrees in your clone of a GitHub repo
• Make sure the 3 worktrees all show in the SCM view
• Open the Pull Requests view and verify that you don't see the same repo 4 times, that you only see it once.