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 a merge directive, use the ``send`` command. For example,
this command creates a merge directive and saves it into the
nominated output file::

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

That file can then be emailed to a reviewer, together with an
explanation of how and why you fixed the problem the way you did, say.

Emailing merge directives is such a common thing that the ``send`` command
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.

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.