There are quite a few paths you might want to get e.g. the repo's path, the worktree's path,
the repo's git dir path, the worktree's git dir path. I want these all obtained once and
then used when needed rather than having to have IO whenever we need them. This is not so
much about reducing time spent on IO as it is about not having to care about errors every time
we want a path.
We now always re-use the state of the repo if we're returning to it, and we always reset the windows to their default tabs.
We reset to default tabs because it's easy to implement. If people want to:
* have tab states be retained when switching
* have tab states specific to the current repo retained when switching back
Then we'll need to revisit this
