Organizing branches
===================

Mirror branches
---------------

A primary difference when using distributed workflows to
develop is that your main local branch is not the place
to make changes. Instead, it is kept as a pristine copy
of the central branch, i.e. it's a *mirror branch*.

To create a mirror branch, set-up a shared repository
(if you haven't already) and then use the ``branch``
(or ``checkout``) command to create the mirror.
For example::

  bzr init-repo PROJECT
  cd PROJECT
  bzr branch bzr+ssh://centralhost/srv/bzr/PROJECT/trunk

Task branches
-------------

Each new feature or fix is developed in its own branch.
These branches are referred to as *feature branches* or
*task branches* - the terms are used interchangeably.

To create a task branch, use the ``branch`` command
against your mirror branch. For example::

  bzr branch trunk fix-123
  cd fix-123
  (hack, hack, hack)

There are numerous advantages to this approach:

 1. You can work on multiple changes in parallel
 2. There is reduced coupling between changes
 3. Multiple people can work in a peer-to-peer mode
    on a branch until it is ready to go.

In particular, some changes take longer to cook than others
so you can ask for reviews, apply feedback, ask for another
review, etc. By completing work to sufficient quality in
separate branches before merging into a central branch, the
quality and stability of the central branch are maintained
at higher level than they otherwise would be.

Refreshing a mirror branch
--------------------------

Use the ``pull`` command to do this::

  cd trunk
  bzr pull

Merging the latest trunk into a feature branch
----------------------------------------------

Use the ``merge`` command to do this::

  cd fix-123
  bzr merge
  (resolve any conflicts)
  bzr commit -m "merged trunk"

Merging a feature into the trunk
--------------------------------

The policies for different distributed workflows vary here.
The simple case where all developers have commit rights to
the main trunk are shown below.

If your mirror is a checkout::

  cd trunk
  bzr update
  bzr merge ../fix-123
  (resolve any conflicts)
  bzr commit -m "Fixed bug #123"

If your mirror is a branch::

  cd trunk
  bzr pull
  bzr merge ../fix-123
  (resolve any conflicts)
  bzr commit -m "Fixed bug #123"
  bzr push

Backing up task branches
------------------------

One of the side effects of centralized workflows is that changes
get frequently committed to a central location which is backed up as
part of normal IT operations. When developing on task branches,
it is a good idea to publish your work to a central location
(but not necessarily a shared location) that will be backed up.
You may even wish to bind local task branches to remote ones
established on a backup server just for this purpose.
