and while there also publish various path. It's easier and better to have all of them exported from here instead of hardcoding them in other files (such as sandbox.c)

dirname(3) is really one of the worst part of POSIX, portability-wise. Implementors can decide to either modify the passed string or return a pointer to an internal storage. The current code fails when dirname returns a pointer to an internal storage because between the strcmp call and the mkdir we go into a recursion that can modify `path'. We can't use copy either because *some* implementation of dirname would have changed that. How to escape from this hell? Take yet another copy of the path!

Use XDG-compliant paths unless ~/.telescope already exists. Provide a script to migrate to XDG-style directory for users who wish to do so.

it's been a while since we're using a lockfile to protect against multiple telescope instances.

During safe_mode the fs process shouldn't open or unlink the crashed_file.

Create a file ~/.telescope/crashed on startup and unlink it on shutdown. If it's present on startup, it means that last time we crashed. It's like the ``dirty'' bit on filesystems to guard for unproper unmounts.

IMSG_GET_FILE handles a path to a local file. fs now behaves like net, it sends a IMSG_GOT_CODE/META and optionally the file. This also includes a bit of refactoring: the send_file function was extracted from handle_get so it can be used in handle_get_file too.