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Bazaar is a tool for helping people collaborate. It does this by
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tracking how a group of files evolves and using that information to help
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people merge their changes together as safely as possible.
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In general, tools that do this are known as revision control systems or
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version control systems (VCS). In the past, VCS tools have been popular
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with software developers. In the future, VCS tools will undoubtedly also be
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important for other groups of people looking to work together on
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files and documents, e.g. technical writers and translators.
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A brief history of version control systems
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------------------------------------------
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VCS tools have been evolving for several decades now. In simple terms,
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there have been 5 generations of tools:
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1. file versioning tools, e.g. SCCS, VCS
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2. tree versioning tools - central style, e.g. CVS
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3. tree versioning tools - central style, done right, e.g. Subversion
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4. tree versioning tools - distributed style, e.g. Arch
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5. tree versioning tools - distributed style, done right, e.g. Bazaar.
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The design and implementation of Bazaar builds on the lessons learned
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from all the previous generations of tools. In particular, Bazaar
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cleanly supports both the central and the distributed version
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control models so you can change models as it makes sense, without
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needing to change tools.
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Central vs distributed VCS
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--------------------------
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Many traditional VCS tools require a central server which provides the
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change history or *repository* for a tree of files. To work on the files,
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users need to connect to the server and *checkout* the files. This gives
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them a directory or *working tree* in which a person can make changes.
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To record or *commit* these changes, the user needs access to the central
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server and they need to unsure they have merged their work with the latest
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version stored before trying to commit. This approach is known as the
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The centralized model has proven useful over time but it can have some notable
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drawbacks. Firstly, a centralized VCS requires that one is able to connect
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to the server whenever one wants to do version control work. Secondly, the
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centralized model tightly links the act of **snapshotting** changes with the act
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of **publishing** those changes. This can be good in some circumstances but
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it has a negative influence on quality in others.
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Distributed VCS tools let users and teams have multiple repositories
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rather than just a single central one. In Bazaar's case, the history is
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normally kept in the same place as the code that is being version controlled.
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This allows the user to commit their changes whenever it makes sense, even
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when offline. Network access is only required when publishing changes or
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when accessing changes in another location.
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In fact, using distributed VCS tools wisely can have advantages well
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beyond the obvious one of disconnected operations for developers.
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Other advantages include:
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* easier for developers to create experimental branches
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* easier ad-hoc collaboration with peers
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* less time required on mechanical tasks - more time for creativity
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* increased release management flexibility through the use of
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"feature-wide" commits
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* trunk quality and stability can be kept higher, making everyone's
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* in open source communities:
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* easier for non-core developers to create and maintain changes
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* easier for core developers to work with non-core developers and
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move them into the core
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* in companies, easier to work with distributed and outsourced teams.
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For a detailed look at the advantages of distributed VCS tools over
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centralized VCS tools, see http://bazaar-vcs.org/BzrWhy.
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Key features of Bazaar
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----------------------
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While Bazaar is not the only distributed VCS tool around, it does have some
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notable features that make it an excellent choice for many teams and
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communities. These include:
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* it **Just Works** - a high focus on usability and performance
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* **adaptive** - cleanly supports many different ways of working together
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* **rich metadata** that tracks merge history across distributed locations,
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understands directories as first-class objects and correctly tracks
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renames of both files and directories
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* **integrated merging** that uses this metadata intelligently to
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ensure that merging is safe without being painful, letting you
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collaborate without fear
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* **truly portable** across many operating systems including Windows
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* **safe with your data** - integrity is checked using cryptographic
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techniques and all changes can be digitally signed if required
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* **low administration**, e.g. access to FTP or SFTP is enough to
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share with others - no special server required
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* **efficiently stores data** across branches in a flexible and safe way
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* an **open architecture and API** that makes it easy to integrate
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* a **large number of plugins** including bzr-svn and GUI front-ends
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* **excellent integration** with a range of companion tools and services
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including PQM, Bundle Buggy and Launchpad
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* **completely open source**
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* **commercial training and support** available from Canonical,
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the company that sponsors Ubuntu.
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While all of these are important, perhaps the greatest asset Bazaar has is
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an active and growing open source community behind it. Bazaar is completely
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free software written in Python so it is easy to contribute improvements.
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Our collective goal is to build and support a distributed VCS tool that
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developers love to use, a tool that helps them get their job done without
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getting in their way. If you wish to get involved, please see
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http://bazaar-vcs.org/Community.
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This manual provides an easy to read introduction to Bazaar and how to use
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it effectively. It is recommended that all users read at least the rest of
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* explains the core concepts users need to know
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* introduces some popular ways of using Bazaar to collaborate.
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Chapters 2-6 provide a closer look at how to use Bazaar to complete
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various tasks. It is recommended that most users read these in first-to-last
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order shortly after starting to use Bazaar. Chapters 7 and beyond provide
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additional information including some recommended best practices.
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This material can be read when required and in any order.
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If you are already familar with other version control tools,
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you may wish to get started quickly by reading the following documents:
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* `Bazaar in five minutes`_ - a mini-tutorial
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* `Bazaar Quick Start Guide`_ - a one page summary of commonly used commands.
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The online help and `Bazaar User Reference`_ are also particularly useful as
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they provide all the gory details on the commands and options available.
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.. _Bazaar in five minutes: ../mini-tutorial/index.html
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.. _Bazaar Quick Start Guide: ../quick-reference/quick-start-summary.svg
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.. _Bazaar User Reference: ../user-reference/bzr_man.html
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We hope you find this manual useful. If you have suggestions on how it
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or the rest of Bazaar's documentation can be improved, please contact
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us on the mailing list, bazaar@lists.canonical.com.
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