~bzr-pqm/bzr/bzr.dev : revision 1964.2.1

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Centralized Workflow

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

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Overview

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========

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This document describes some basic workflow for using Bazaar_. This doesn't

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try to explain *why* every step is done, but more gives recommendations

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about what is considered a good way to work with Bazaar_.

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Bazaar_ is designed to be very flexible in workflows, from fully

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decentralized to mostly centralized.

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The practices here are meant to help ease the user into more advanced usage

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of Bazaar_, and allowing them to work in a mix of centralized and

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decentralized operation.

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In general, this document is meant for people in a work setting. Where

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several people are working on the same codebase, and want to work with

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eachother and keep in sync. However, this workflow is also applicable to a

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single developer, who might work on several machines, and wants to keep in

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sync with themselves.

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.. _Bazaar: http://bazaar-vcs.org

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Initial Setup

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

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These are some reasonably simple steps to setup Bazaar_ so that it works

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well for you.

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Setting User Email

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------------------

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Your user identity is stored with each commit. While this doesn't have to

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be accurate, unique, or anything else, it will be used in log messages an

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annotations, so it is nice to have something real.::

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% bzr whoami "John Doe <jdoe@organization.com>"

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Setting up a local Repository

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-----------------------------

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Bazaar_ branches generally copy the history information around with them,

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which is part of how you can work in a fully decentralized manner. As an

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optimization, it is possible for branches to combine their storage needs,

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so that you do not need to copy around all of this history information

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whenever you create a new branch.

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The best way to do this is to create a `Shared Repository`_. In general,

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branches will share their storage if they exist in a subdirectory of a

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`Shared Repository`_. So lets setup a `Shared Repository`_ in our home

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directory, thus all branches we create underneath will share their history

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storage.::

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% bzr init-repo --trees ~

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Setting up a remote Repository

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------------------------------

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Many times you want a location where data is stored separate from where

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you do your work. This workflow is required by centralized systems (CVS/SVN).

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Usually they are on separate machines, but not always. This is actually a

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pretty good setup, especially in a work environment. Because it ensures

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a central location where data can be backed up, and means that if something

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happens to a developer's machine, no committed work has been lost.

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So lets set up a shared location for our project. Again, we will use a

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`Shared Repository`_ to optimize disk usage.::

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% bzr init-repo --no-trees sftp://centralhost/srv/bzr/

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You can think of this step as similar to setting up a new cvsroot, or

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subversion repository (only obviously it is a little bit simpler).

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Starting to version an existing project

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

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Now that we have a repository, lets get going with a new project. Most of

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the time, you will already have some code that you started working with,

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that you now want to version using Bazaar_. If the code was originally

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in source control, there are many ways to convert the project to Bazaar_

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without losing any history. However, this is outside of the scope of this

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document. See XXXReferenceConversionOfHistory_.

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Developer 1: Creating the first revision

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----------------------------------------

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So first, we want to create a branch in our remote Repository, where we

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will want to host the project. Let's assume we have a project named

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"sigil" that we want to start versioning, and create an empty branch::

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% bzr init sftp://centralhost/srv/bzr/sigil

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This can be thought of as the "HEAD" branch in CVS terms, or as the "trunk"

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in Subversion terms. We typically call this the ``dev`` branch.

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I prefer working in a subdirectory of ``$HOME`` to avoid collisions with all

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the other stuff that ends up in ``$HOME``. Also, we will want a project

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directory where we can hold all of the different branches we end up

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working on::

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% cd ~

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% mkdir work

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% cd work

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% mkdir sigil

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% cd sigil

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% bzr checkout sftp://centralhost/srv/bzr/sigil dev

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% cd dev

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% cp -ar ~/sigil/* .

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% bzr add

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% bzr commit -m "Initial import of Sigil"

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There are many ways to setup your working directory, but the above way

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will makes it easy to handle working with feature/bugfix branches. And one

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of the strong points of Bazaar_ is how well it works with branches.

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At this point, because you have a 'checkout' of the remote branch, any

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commits you make in ``dev/`` will automatically be saved both locally,

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and on ``centralhost``.

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Developer N: Getting a working copy of the project

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--------------------------------------------------

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Since the first developer did all of the work of creating the project,

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all other developers can just get a checkout of that branch. They should

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still follow `Setting User Email`_ and `Setting up a local Repository`_.

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Then to get a copy of the current tip::

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% cd ~/work/sigil

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% bzr checkout sftp://centralhost/srv/bzr/sigil dev

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Now that two people both have a checkout of

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``sftp://centralhost/srv/bzr/sigil``, there will be times when one of

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them is out of date with the current version. Bazaar_ will inform the user

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of this and prevent them from committing. To get up to date use ``bzr

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update``, which will update the tree with the remote changes. This may

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require resolving conflicts, in the case that the same files have been

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modified.

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Developing on separate branches

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

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So far everyone is working and committing their changes into the same

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branch. Which means that everyone needs to update fairly regularly, and

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deal with other people's changes. Also, if one person commits something

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which breaks the codebase, then everyone has to deal with it.

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Usually, it is better to do development on individual branches, and then

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integrate those back into the main branch, once they are stable. This is

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one of the biggest changes from working with CVS/SVN. They both allow you

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to work on separate branches, but their merging algorithms are fairly

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weak, so it is difficult to keep things synchronized. Bazaar_ merges track

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what has already been merged, and can even apply changes to files that

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have been renamed.

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Creating and working on a new branch

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We want to keep our changes available for other people, even if they

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aren't quite complete yet. So we will create a new public branch, and

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track it locally.::

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% cd ~/work/sigil

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% bzr branch sftp://centralhost/srv/bzr/sigil \

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sftp://centralhost/srv/bzr/sigil/doodle-fixes

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% bzr checkout sftp://centralhost/srv/bzr/sigil/doodle-fixes doodle-fixes

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% cd doodle-fixes

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We now have a place to make any fixes to doodles that we need. And we

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won't interrupt people who are working on other parts of the code.

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Because we have a checkout, any commits made in the ``doodle-fixes/`` will

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also show up on ``centralhost``.

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It is also completely possible to have 2 developers collaborate on one of

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these branches, just like they would have collaborated on the ``dev``

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branch.[#cbranch]_

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.. [#cbranch] When using lots of independent branches, having to retype

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the full URL all the time takes a lot of typing. We are looking into

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various methods to help with this, such as branch aliases, etc. For

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now, though, the bzrtools_ plugin provides the ``bzr cbranch`` command.

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Which is designed to take a base branch, create a new public branch,

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and create a checkout of that branch, all with much less typing.

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Configuring ``cbranch`` is outside the scope of this document, but the

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final commands look like ``bzr cbranch dev my-feature-branch``

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.. _bzrtools: https://launchpad.net/products/bzrtools

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Merging changes back

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When it is decided that some of the changes in ``doodle-fixes`` is ready

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to be merged into the main tree, simply do::

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% cd ~/work/sigil/dev

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% bzr merge ../doodle-fixes

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Now the changes are available in the ``dev`` branch, but they haven't been

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committed yet. This is the time when you want to review the final changes,

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and make sure they are what you want. ``bzr status`` and ``bzr diff`` are

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good tools to use here. Also, there may be some conflicts in files, if

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there were changes made to the same file. Bazaar_ will prevent you from

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committing until you have resolved these conflicts. That way you don't

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accidentally commit the conflict markers. ``bzr status`` will show the

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conflicts along with the other changes, or you can use ``bzr conflicts``

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to just list conflicts. Use ``bzr resolve file/name`` or ``bzr resolve

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--all`` once conflicts have been handled.[#resolve]_

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If you have a conflict that is particularly difficult to solve you may

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want to use the ``bzr remerge`` command. It will let you try different

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merge algorithms, as well as let you see the original source lines

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(``--show-base``).

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.. [#resolve] Some systems make you resolve conflicts as part of the merge

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process. We have found that it is usually easier to resolve conflicts

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when you have the view of the entire tree, rather than just a single

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file. It gives you much more context, and also lets you run tests as

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you resolve the problems.

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Recommended Branching

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One very common way to handle all of these branches is to give each

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developer their own branch, and their own place to work in the central

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location. This can be done with::

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% bzr branch sftp://centralhost/srv/bzr/sigil \

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sftp://centralhost/srv/bzr/sigil/user-a

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% bzr branch sftp://centralhost/srv/bzr/sigil \

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sftp://centralhost/srv/bzr/sigil/user-b

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This gives each developer their own branch to work on. And, they can

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easily create a new feature branch for themselves with just[#cbranch]_::

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% bzr branch sftp://centralhost/srv/bzr/sigil/user-a \

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sftp://centralhost/srv/bzr/sigil/user-a/feature

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% cd ~/work/sigil

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% bzr checkout sftp://centralhost/srv/bzr/sigil/user-a/feature myfeature

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Glossary

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========

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Shared Repository

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-----------------

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Bazaar_ has the concept of a `Shared Repository`_. This is similar to the

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concept of other RCS's repository. Such as in Subversion, where you have a

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remote repository, which is where all of the history is stored, and

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locally you don't have any history information, only a checkout of the

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working tree files. Note that "Shared" in this context means shared

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between branches. It *may* be shared between people, but standalone

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branches can also be shared between people.

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In Bazaar_ terms, a `Shared Repository`_ is a location where multiple

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branches can **share** their revision history information. Because Bazaar_

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wants to support decentralized workflows, it is possible for every branch

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to maintain its own revision history information. But this is often

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inefficient, since often branches share history, and they might as well

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share the storage as well.

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..

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vim: tw=74 ft=rst spell spelllang=en_us