Post #1496102

@dascandy @cyphar @brauner Decide: Which one is correct? Bonus points: What happens if I delete the `aa` subtree and then subsequently do `cd ..` in the shell? According to the kernel the shell process is within the `bb` tree. The shell "thinks" it's all over both trees. We could of course define that the kernel's view of things (as exposed by proc) is the ultimate truth, but this would break a lot of programs with different interpretations.