Linux Tor Browser should not store data in the Browser (application) directory

We want to move to a model on all platforms where user data is not stored in the application area. This is the Linux-specific ticket. See #13252 (moved) for the original, Mac-specific ticket.

added component::applications/tor browser owner::mcs parent::20599 priority::medium severity::normal status::new type::defect labels

Trac:
Cc: brade to brade, gk

See the comment thread here for another problem this will solve: https://blog.torproject.org/blog/tor-browser-602-released#comment-187765

Trac:
Reviewer: N/A to N/A

Trac:
Parent: N/A to #20599 (moved)

See #20497 (moved) for a related ticket. Also, if there is a chance that the user data might be stored in a shared location such as the user's home directory, then we need to account for the last issue raised by Arthur in ticket:13252#comment:57 after all, i.e., we may need to embed the app path in the update directory (like we do on OSX) in order to ensure that the update history is partitioned.

Under this model, how does updating work? If it moves beyond "Download the MAR and update it like upstream firefox", then I'd need documentation on how to replicate the other steps for the whole "the sandboxing helper needs to handle installation/updates" use case.

Something I can set at runtime to force existing behavior would also work I guess...

Trac:
Cc: brade, gk to brade, gk, yawning

I think it will solve #25663 (moved) as well where corrupted downloads during updates got reported.

Trac:
Cc: brade, gk, yawning to brade, gk, yawning, dgr

mentioned in issue #19646 (moved)

mentioned in issue #21301 (moved)

mentioned in issue #25663 (moved)

mentioned in issue #25663 (moved)

mentioned in issue #28640 (moved)

mentioned in issue #28640 (moved)

mentioned in issue #28640 (moved)

moved to tpo/applications/tor-browser#18369