Sending changes
===============

Motivation
----------

In many distributed development scenarios, it isn't always feasible for
developers to share task branches by advertising their URLs.
For example, a developer working on a laptop might take it home overnight
so his/her task branches could well be inaccessible when a gatekeeper
in another timezone wants to review or merge it.

Bazaar provides a neat feature to assist here: *merge directives*.

Understanding merge directives
------------------------------

You can think of a merge directive as a "mini branch" - just the
new growth on a branch since it was created. It's a software
patch showing what's new but with added intelligence: metadata
like interim commits, renames and digital signatures.

Another useful metaphor is a packet cake: a merge directive has a recipe
together with the ingredients you need bundled inside it.
To stretch the metaphor, the ingredients are all the metadata on the
changes made to the branch; the recipe is instructions on how those
changes ought to be merged, i.e. information for the ``merge`` command
to use in selecting common ancestors.

Regardless of how you think of them, merge directives are neat.
They are easy to create, suitable for mailing around as attachments
and can be processed much like branches can on the receiving end.

Creating a merge directive
--------------------------

To create and optionally send a merge directive, use the ``send`` command. 

By default, ``send`` will email the merge directive to the "submission
address" for the branch, which is typically the lead developer or the
development mailing list.  
``send`` without options will create a merge directive, fire up your email
tool and attach it, ready for you to add the explanatory text bit.
(See the online help for ``send`` and
`Configuration Settings <../user-reference/bzr_man.html#configuration-settings>`_
in the User Reference for further details on how to configure this.)

Most projects like people to add some explanation to the mail along with
the patch, explaining the reason for the patch, and why it is done the way
it is.  This gives a reviewer some context before going into the
line-by-line diff.

Alternatively, if the ``--output`` (or ``-o``) option is given, ``send``
will write the merge directive to a file, so you can mail it yourself,
examine it, or save it for later use.  If an output file of ``-`` is
given, the directive is written to stdout.  For example::

  cd X-fix-123
  bzr send -o ../fix-123.patch


Applying a merge directive
--------------------------

Merge directives can be applied in much the same way as branches: by
using the ``merge`` and ``pull`` commands.

They can also be useful when communicating with upstream projects
that don't use Bazaar. In particular, the preview of the overall
change in a merge directive looks like a vanilla software patch, so
they can be applied using ``patch -p0`` for example.
