New iteration behavior via FileIter and TreeWalker

Instead of returning a channel of files, Tree.Files() now returns a
FileIter with these qualities:

* It returns files in the original order of the repository (relying on a
* new Tree.OrderedNames property)
* It can return errors encountered when retrieving files and trees from
* underlying storage
* It can be Closed without having to drain the entire channel
* It defers the heavy lifting to a new TreeWalker type
* Its behavior is a little more consistent with other Iter types
* It's a little less prone to memory leaks

This update includes a new TreeWalker type that will iterate through all
of the entries of a tree and its descendant subtrees. It does the dirty
work that Tree.walkEntries() used to do, but with a public API.

A new TreeIter type is also included that just walks through subtrees.
This could be useful for performing a directory search while ignoring
files/blobs altogether.

0 files changed, 0 insertions, 0 deletions