fix sandbox wrt XDG-style directories

move declarations from telescope.h in fs.h 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 fix 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!

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

delete old (and wrong) comment it's been a while since we're using a lockfile to protect against multiple telescope instances.

sync changelog

fix patch syntax highlighting wrt multiple headers

sort includes

spend a few more words describing on how the safe mode works

ignore the crashed file if in safe_mode During safe_mode the fs process shouldn't open or unlink the crashed_file.

propagate the safe_mode to the children

don't acquire the file lock in safe_mode

mention -C in usage()

sync

add a safe/sandbox mode When enabled with the -S (or --safe) flag, prevent telescope from writing files to the disk.