~bzr-pqm/bzr/bzr.dev

What is a Plugin

================

A plugin is an external component for Bazaar-NG that is typically made by

third parties. A plugin is capable of augmenting Bazaar-NG by adding or

replacing new or current functionality in Bazaar-NG. Plugins often work as

a way for developers to test new features for Bazaar-NG prior to inclusion

in the official codebase. Plugins can do a variety of things, including

overriding commands, adding new commands, providing additional network

transports, customizing log output. The sky is the limit for the

customization that can be done through plugins.

Where to find Plugins 

=====================

We keep our list of plugins on the http://bazaar-vcs.org/PluginRegistry page.

Writing a plugin

================

Plugins are very similar to bzr core functionality.  They can import

anything in bzrlib.  A plugin may simply override standard functionality,

but most plugins supply new commands.

To create a command, make a new object that derives from

`bzrlib.commands.Command`, and name it cmd_foo, where foo is the name of

your command.  If you create a command whose name contains an underscore,

it will appear in the UI with the underscore turned into a hyphen.  For

example, "cmd_baz_import" will appear as "baz-import".  For examples of how

to write commands, please see builtins.py.

Once you've created a command you must register the command with

`bzrlib.commands.register_command(cmd_foo)`.  You must register the command

when your file is imported, otherwise bzr will not see it.

Bzr will scan **bzrlib/plugins** and **~/.bazaar/plugins** for plugins by

default.  You can override this with **BZR_PLUGIN_PATH**.  Plugins may be

either modules or packages.  If your plugin is a single file, you can

structure it as a module.  If it has multiple files, or if you want to

distribute it as a bzr branch, you should structure it as a package, i.e. a

directory with an **__init__.py** file.

Please feel free to contribute your plugin to BzrTools, if you think it

would be useful to other people.

How to Install a plugin 

=======================

Installing a plugin is very easy! One can either install a plugin

systemwide or on a user by user basis. Both methods involve create a

"plugins" directory. Within this directory one can place plugins in

subdirectories. For example, "plugins/bzrtools/".

Two locations are currently checked; the bzrlib/plugins directory

(typically found in /usr/lib/python2.4/site-packages/bzrlib/plugins/) and

$HOME/.bazaar/plugins/.

One can additionally override the home plugins by setting the environment

variable BZR_PLUGIN_PATH to a directory that contains plugins. The

installation of a plugin can be checked by running **bzr plugins** at

any time. New commands can be seen by running **bzr help commands**.

Plugins work particularly well with Bazaar-NG branches. For example, to

install the bzrtools plugins for your main user account, one can perform

the following:: 

    bzr branch http://panoramicfeedback.com/opensource/bzr/bzrtools

    ~/.bazaar/plugins/bzrtools