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Hacking BE
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Adding commands
===============

To write a plugin, you simply create a new file in the
``libbe/commands/`` directory.  Take a look at one of the simpler
plugins (e.g. ``remove.py``) for an example of how that looks, and to
start getting a feel for the libbe interface.

See ``libbe/commands/base.py`` for the definition of the important
classes ``Option``, ``Argument``, ``Command``, ``InputOutput``,
``StorageCallbacks``, and ``UserInterface`` classes.  You'll be
subclassing ``Command`` for your command, but all those classes will
be important.


Command completion
------------------

BE implements a general framework to make it easy to support command
completion for arbitrary plugins.  In order to support this system,
any of your completable ``Argument()`` instances (in your command's
``.options`` or ``.args``) should be initialized with some valid
completion_callback function.  Some common cases are defined in
``libbe.command.util``.  If you need more flexibility, see
``libbe.command.list``'s ``--sort`` option for an example of
extensions via ``libbe.command.util.Completer``, or write a custom
completion function from scratch.


Adding user interfaces
======================

Take a look at ``libbe/ui/command_line.py`` for an example.  Basically
you'll need to setup a ``UserInterface`` instance for running commands.
More details to come after I write an HTML UI...


Testing
=======

Run any tests in your module with::

    be$ python test.py <python.module.name>

for example:

    be$ python test.py libbe.command.merge

For a definition of "any tests", see ``test.py``'s
``add_module_tests()`` function.

Note that you will need to run ``make`` before testing a clean BE
branch to auto-generate required files like ``libbe/_version.py``.


Profiling
=========

Find out which 20 calls take the most cumulative time (time of
execution + childrens' times)::

    $ python -m cProfile -o profile be [command] [args]
    $ python -c "import pstats; p=pstats.Stats('profile'); p.sort_stats('cumulative').print_stats(20)"

It's often useful to toss::

    import sys, traceback
    print >> sys.stderr, '-'*60, '\n', '\n'.join(traceback.format_stack()[-10:])

into expensive functions (e.g. ``libbe.util.subproc.invoke()``) if
you're not sure why they're being called.