~bzr-pqm/bzr/bzr.dev

bzr-svn

=======

Overview

--------

bzr-svn lets developers use Bazaar as their VCS client on projects

still using a central Subversion repository. Access to Subversion

repositories is largely transparent, i.e. you can use most ``bzr``

commands directly on Subversion repositories exactly the same

as if you were using ``bzr`` on native Bazaar branches.

Many bzr-svn users create a local mirror of the central Subversion

trunk, work in local feature branches, and submit their

overall change back to Subversion when it is ready

to go. This lets them gain many of the advantages of distributed

VCS tools without interrupting existing team-wide processes and

tool integration hooks currently built on top of Subversion. Indeed,

this is a common interim step for teams looking to adopt Bazaar but

who are unable to do so yet for timing or non-technical reasons.

For installation instructions, see the bzr-svn home page:

http://bazaar-vcs.org/BzrForeignBranches/Subversion.

A simple example

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

Here's a simple example of how you can use bzr-svn to hack on a

GNOME project like **beagle**. Firstly, setup a local shared repository

for storing your branches in and checkout the trunk::

  bzr init-repo --default-rich-root beagle-repo

  cd beagle-repo

  bzr checkout svn+ssh://svn.gnome.org/svn/beagle/trunk beagle-trunk

Note that using the ``default-rich-root`` option to ``init-repo`` is

important as bzr-svn requires some extra metadata not yet supported in Bazaar's

default repository format. Next, create a feature branch and hack away::

  bzr branch beagle-trunk beagle-feature1

  cd beagle-feature1

  (hack, hack, hack)

  bzr commit -m "blah blah blah"

  (hack, hack, hack)

  bzr commit -m "blah blah blah"

When the feature is cooked, refresh your trunk mirror and merge

your change::

  cd ../beagle-trunk

  bzr update

  bzr merge ../beagle-feature1

  bzr commit -m "Complete comment for SVN commit"

As your trunk mirror is a checkout, committing to it implicitly

commits to the real Subversion trunk. That's it!

Using a central repository mirror

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

For large projects, it often makes sense to tweak the recipe given above.

In particular, the initial checkout can get quite slow so you may wish

to import the Subversion repository into a Bazaar one once and for all

for your project, and then branch from that native Bazaar repository

instead. bzr-svn provides the ``svn-import`` command for doing this

repository-to-repository conversion. Here's an example of how to use it::

  bzr svn-import svn+ssh://svn.gnome.org/svn/beagle

Here's the recipe from above updated to use a central Bazaar mirror::

  bzr init-repo --default-rich-root beagle-repo

  cd beagle-repo

  bzr branch bzr+ssh://bzr.gnome.org/beagle.bzr/trunk beagle-trunk

  bzr branch beagle-trunk beagle-feature1

  cd beagle-feature1

  (hack, hack, hack)

  bzr commit -m "blah blah blah"

  (hack, hack, hack)

  bzr commit -m "blah blah blah"

  cd ../beagle-trunk

  bzr pull

  bzr merge ../beagle-feature1

  bzr commit -m "Complete comment for SVN commit"

  bzr push

In this case, committing to the trunk only commits the merge locally.

To commit back to the master Subversion trunk, an additional command

(``bzr push``) is required.

Note: You'll need to give ``pull`` and ``push`` the relevant URLs

the first time you use those commands in the trunk branch. After that,

bzr remembers them.

The final piece of the puzzle in this setup is to put scripts in

place to keep the central Bazaar mirror synchronized with the Subversion

one. This can be done by adding a cron job, using a Subversion hook,

or whatever makes sense in your environment.

Limitations of bzr-svn

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

Bazaar and Subversion are different tools with different capabilities

so there will always be some limited interoperability issues.

Here are some examples current as of bzr-svn 0.5.4:

 * Bazaar doesn't support versioned properties

 * Bazaar doesn't support tracking of file copies.

See the bzr-svn web page,

http://bazaar-vcs.org/BzrForeignBranches/Subversion,

for the current list of constraints.