Following the large refactor on the previous commit, this commit fixes
the reverse functionality.
Depth detection moved into the tree building instead of being calculated
when drawing the tree to screen
WIP
Replace array of (string, int) pairs with tree of nodes.
A tree of nodes more accurately represents the underlying file structure
and hence is a better fit for the problem space.
Regression: Reverse doesn't work in this commit.
I suspect more methods can be simplifed and reduced.
strip_end_slash_including_root will remove end slashes including the
root directory.
The root directory has been a long running problem because if we strip
the final slash we will run dust on no directory instead of the root.
dust sort is now more predictable as it orders first by size and second
by name.
Walkdir still gives different iteration orders on different systems so
all output is not entirely predictable
Advised to use walkdir by burntsushi as using recursion on file systems
can blow the stack.
walkdir is slower but allows the code to be cleaner and more reliable
Also experimented with ignore but locking the hashmap resulted in
similar performance to walkdir but with much uglier code.
andy.boot
Joe Ardent