~bzr-pqm/bzr/bzr.dev

Upgrades

========

Bazaar has a strong commitment to inter-version compatibility both on disk and

over the network.  Newer clients should be able to interact with older

versions on the server (although perhaps not at optimal speed) and older

clients should also be able to communicate with newer versions of Bazaar on

the server.  Divergences from this rule are considered bugs and are fixed in

later versions.

That said, Bazaar is constantly improving and the most recent versions are the

most featureful and have better performance.  In particular, the Bazaar

versions 2.0 and later have significant advantages over earlier versions,

including a more compact disk format, faster network operations and overall

performance improvements.  With the 2.0 release, Bazaar has moved to a

stable/development release model where the 2.x series is maintained with

bugfixes releases for six months, while simultaneously the 2.(x+1) series is

being developed with monthly beta releases that are suitable for everyday use.

Bazaar development has a stable trunk with an extensive test suite, so there

is no reason to fear using the development series for everyday use, it simply

changes more often than the stable series.  Many users do run the development

version of Bazaar and update it regularly, including most of the Bazaar

developers themselves.

Software upgrades

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

Upgrading the Bazaar software is as simple as re-installing the Python package

using either the latest binary package for Windows or Mac OS X, the binary

package provided by your GNU/Linux distribution, or installing from the source

release.  See http://wiki.bazaar.canonical.com/Downloads for the latest

releases for all supported platforms.

Bazaar's later versions support all of the earlier disk formats (back to the

very first one), so there is no need to upgrade the branches on the disk when

upgrading the software.  To make use of particular new features that might

need updated versions on both the server and developer's machines, it does not

matter if the clients or the servers are upgraded first.

Disk format upgrades

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

In its evolution, Bazaar has used a sequence of disk formats for improved

storage efficiency and speed.  With the new disk format released in version

2.0, there is a commitment to keep that disk format until version 3.0 is

released, which has not even been planned yet.  (Bazaar 2.0 was released

almost two years after Bazaar 1.0.)  As a result, disk format upgrades should

be extremely infrequent.

If there are existing branches in an older format that you would like to

upgrade to the latest format, you can see the `2.0 Upgrade Guide

<../upgrade-guide/index.html>`_ for more information.  From the system

administration perspective, it is important to coordinate the timing of

various upgrades in the process.  First, the central branches on the server

should be upgraded.  Next, any local mirrors that developers have should be

upgraded.  Finally, developers' local branches should be upgraded.  These

upgrades will require an appropriate version of the software whenever they are

performed.  (It is possible to upgrade branches remotely over the network, but

it may be much slower.)

Plugin upgrades

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

When Bazaar does update its version, plugins that use the Bazaar API may need

to be upgraded to reflect changes in that API.  Some plugins have strict

version dependencies on the version of the Bazaar API that they will accept.

If this is the case, then you should ensure that the plugins you depend on

have been updated *before* you upgrade your Bazaar version to avoid a

situation where your plugins won't work with the installed version of Bazaar.

If this does happen, then the solution is simply to reinstall the previous

version of Bazaar that *did* work with the plugins.  For installations that

depend on a large number of plugins, this sort of version upgrade should be

tested in a safe sandbox to ensure that the entire collection of Bazaar and

its plugins can all work together.