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Closes #1944
Closes #3315

* Added autocomplete support for local knife file uploads

* Added option to allow for relative path resolution for cookbooks

* Updated _chef_root function to use directory:h

* added new commands 'diff' and 'upload'
* Add basic file completion for file-centric commands 'diff' and
  'upload'

this is useful when managing multiple chef servers

This commit adds the --format tag to all of the autocompletion functions. The default format changed from json to a "human readable" format as of version 0.10.  This change should be backward compatible.  Alternatively, these commands could be simplified by using the new default human readable format.