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In many distributed development scenarios, it isn't always feasible for
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developers to share task branches by advertising their URLs.
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For example, a developer working on a laptop might take it home overnight
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so his/her task branches could well be inaccessible when a gatekeeper
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in another timezone wants to review or merge it.
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Bazaar provides a neat feature to assist here: *merge directives*.
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Understanding merge directives
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------------------------------
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You can think of a merge directive as a "mini branch" - just the
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new growth on a branch since it was created. It's a software
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patch showing what's new but with added intelligence: metadata
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like interim commits, renames and digital signatures.
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Another useful metaphor is a packet cake: a merge directive has a recipe
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together with the ingredients you need bundled inside it.
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To stretch the metaphor, the ingredients are all the metadata on the
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changes made to the branch; the recipe is instructions on how those
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changes ought to be merged, i.e. information for the ``merge`` command
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to use in selecting common ancestors.
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Regardless of how you think of them, merge directives are neat.
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They are easy to create, suitable for mailing around as attachments
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and can be processed much like branches can on the receiving end.
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Creating a merge directive
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--------------------------
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To create and optionally send a merge directive, use the ``send`` command.
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By default, ``send`` will email the merge directive to the "submission
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address" for the branch, which is typically the lead developer or the
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development mailing list.
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``send`` without options will create a merge directive, fire up your email
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tool and attach it, ready for you to add the explanatory text bit.
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(See the online help for ``send`` and
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`Configuration Settings <../user-reference/configuration-help.html>`_
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in the User Reference for further details on how to configure this.)
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Most projects like people to add some explanation to the mail along with
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the patch, explaining the reason for the patch, and why it is done the way
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it is. This gives a reviewer some context before going into the
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Alternatively, if the ``--output`` (or ``-o``) option is given, ``send``
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will write the merge directive to a file, so you can mail it yourself,
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examine it, or save it for later use. If an output file of ``-`` is
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given, the directive is written to stdout. For example::
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bzr send -o ../fix-123.patch
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Applying a merge directive
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--------------------------
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Merge directives can be applied in much the same way as branches: by
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using the ``merge`` and ``pull`` commands.
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They can also be useful when communicating with upstream projects
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that don't use Bazaar. In particular, the preview of the overall
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change in a merge directive looks like a vanilla software patch, so
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they can be applied using ``patch -p0`` for example.