Workflows
=========

Bazaar is just a tool
---------------------

Bazaar supports many different ways of working together.
This means that you can
start with one workflow and adapt it over time as circumstances
change. There is no "one true way" that always makes sense and
there never will be. This section provides a brief overview of
some popular workflows supported by Bazaar.

Keep in mind that these workflow are just *some* examples of how
Bazaar can be used. You may want to use a workflow not listed here,
perhaps building on the ideas below.

Solo
----

Whether developing software, editing documents or changing configuration files,
having an easy-to-use VCS tool can help. A single user can use this workflow
effectively for managing projects where they are the only contributor.

.. image:: images/workflows_single.png

Advantages of this workflow over not using version control at all include:

 * backup of old versions
 * rollback to an earlier state
 * tracking of history.

The key features of Bazaar appropriate for this workflow are low administration
(no server setup) and ease of use.


Partner
-------

Sometimes two people need to work together sharing changes as they go. This
commonly starts off as a *Solo* workflow (see above) or a team-oriented
workflow (see below). At some point, the second person takes a branch (copy
including history) of what the first person has done. They can then work in
parallel exchanging changes by merging when appropriate.

.. image:: images/workflows_peer.png

Advantages over *Solo* are:

 * easier sharing of changes
 * each line of each text file can be attributed to a particular change
   including who changed it, when and why.

When implementing this workflow, Bazaar's advantages over CVS and Subversion include:

 * no server to setup
 * intelligent merging means merging multiple times isn't painful.


Centralized
-----------

Also known as *lock-step*, this is essentially the same as the workflow
encouraged/enforced by CVS and Subversion. All developers work on the same
branch (or branches). They run ``bzr update`` to get their checkout up-to-date,
then ``bzr commit`` to publish their changes to the central location.

.. image:: images/workflows_centralized.png

Subversion and CVS are good choices for implementing this workflow because they
make it easy. Bazaar directly supports it as well while providing some
important advantages over CVS and Subversion:

 * better branching and merging
 * better renaming support.


Centralized with local commits
------------------------------

This is essentially the same as the *Centralized* model, except that when
developers are making a series of changes, they do ``commit --local`` or unbind
their checkout. When it is complete, they commit their work to the shared
mainline.

.. image:: images/workflows_localcommit.png

Advantages over *Centralized*:

 * Can work offline, e.g. when disconnected during travel
 * Less chance for a bad commit to interfere with everyone else's work

Subversion and CVS do not support this model. Other distributed VCS tools can
support it but do so less directly than Bazaar does.


Decentralized with shared mainline
----------------------------------

In this workflow, each developer has their own branch or branches, plus commit
rights to the main branch. They do their work in their personal branch, then
merge it into the mainline when it is ready.

.. image:: images/workflows_shared.png

Advantage over *Centralized with local commits*:

 * Easier organization of work - separate changes can be developed in their own branches
 * Developers can merge one another's personal branches when working on something together.

Subversion and CVS do not support this model. Other distributed VCS
tools support it. Many features of Bazaar are good for this workflow
including ease of use, shared repositories, integrated merging and
rich metadata (including directory rename tracking).


Decentralized with human gatekeeper
-----------------------------------

In this workflow, each developer has their own branch or branches, plus
read-only access to the main branch. One developer (the gatekeeper) has commit
rights to the main branch. When a developer wants their work merged, they ask
the gatekeeper to merge it. The gatekeeper does code review, and merges the
work into the main branch if it meets the necessary standards.

.. image:: images/workflows_gatekeeper.png

Advantage over *Decentralized with shared mainline*:

 * Code is always reviewed before it enters the mainline
 * Tighter control over when changes get incorporated into the mainline.

A companion tool of Bazaar's called Bundle Buggy can be very useful for
tracking what changes are up for review, their status and reviewer comments.


Decentralized with automatic gatekeeper
---------------------------------------

In this workflow, each developer has their own branch or branches, plus
read-only access to the mainline. A software gatekeeper has commit rights to
the main branch. When a developer wants their work merged, they request another
person to review it. Once it has passed review, either the original author or
the reviewer asks the gatekeeper software to merge it, depending on team
policies. The gatekeeper software does a merge, a compile, and runs the test
suite. If and only if the code passes, it is merged into the mainline.

Note: As an alternative, the review step can be skipped and the author can
submit the change to the automatic gatekeeper without it. (This is particularly
appropriate when using practices such as Pair Programming that effectively
promote just-in-time reviews instead of reviewing code as a separate step.)

.. image:: images/workflows_pqm.png

Advantages over *Decentralized with human gatekeeper*:

 * Code is always tested before it enters the mainline (so the integrity of the
   mainline is higher)
 * Scales better as teams grow.

A companion tool of Bazaar's called Patch Queue Manager (PQM) can provide the
automated gatekeeper capability.


Implementing a workflow
-----------------------

For an in-depth look at how to implement each of the workflows above,
see chapters 3 to 6 in this manual. First though, chapter 2
explains some important pre-requisites including installation, general
usage instructions and configuration tips.
