Tree Walking

Tree Walking is the traversing of a file system, a tree of files. It's a common operation on many types of DirectedAcyclicGraphs

In Unix, many commands implement a -r or -R operation to do something recursively, as in all files here and ditto for all subdirectories hereunder. It gets tricky (read Hacky) when some of those directories are mount points or devices. TreeWalking is found in the commands du, cp, find, grep, chmod, scp, ls, tar, cpio, (please add more)...

A bunch of implementations, all different, without a library behind them -- over ripe for a ReFactoring. However, with all the various histories of the above commands, a single, simple tree walk is insufficient. How do we do DepthFirst, BreadthFirst, and other of these TreeWalking functions.

Contributors: ChrisGarrod (Just wait till he fills in how PlanNine does TreeWalking)