Add
===

Add is used to recursively version some paths supplied by the user. Paths that
match ignore rules are not versioned, and paths that become versioned are
versioned in the nearest containing bzr tree. Currently we only do this within
a single tree, but perhaps with nested trees this should change.

Least work we can hope to perform
---------------------------------

* Read a subset of the full versioned paths data for the tree matching the scope of the paths the user supplied.
* Seek once to each directory within the scope and readdir its contents.
* Probe if each directory is a child tree to avoid adding data for paths within a child tree.
* Calculate the ignored status for paths not previously known to be ignored
* Write data proportional to the newly versioned file count to record their versioning.
* Assign a fileid for each path (so that merge --uncommitted can work immediately)

Optionally:

* Print the ignore rule for each ignored path in the scope.
* Print the path of each added file.
* Print the total count of ignored files within the scopes.
* Record the result of calculating ignored status for ignored files.
  (proportional to the number we actually calculate).

Per file algorithm
------------------

#. If the path is versioned, and it is a directory, push onto the recurse stack.
#. If the path is supplied by the user or is not ignored, version it, and if a
   directory, push onto the recurse stack. Versioning the path may require
   versioning the paths parents.
#. Output or otherwise record the ignored rule as per the user interface selected.
