***********************************
What's New in Bazaar 2.4 (Oronsay)?
***********************************

Bazaar 2.4 is still under development, and will be released in August 2011.
This document accumulates a high level summary of what's changed.  See the
:doc:`../release-notes/index` for a full list.

Users are encouraged to upgrade from the other stable series.  This
document outlines the improvements in Bazaar 2.4 vs Bazaar 2.3. As well as
summarizing improvements made to the core product, it highlights
enhancements within the broader Bazaar world of potential interest to
those upgrading.

Bazaar 2.4.0 is fully compatible both locally and on the network with 2.0,
2.1, 2.2 and 2.3, and can read and write repositories generated by all
previous versions.

Dropping Python2.4 and Python2.5 support
****************************************

Bazaar 2.4.0 is the first version of bzr to drop support for python
versions before 2.6. The 2.3 series will still be maintained in bugfix
mode for people who need older versions of python. You can also use
Launchpad to nominate fixes for 2.3. We can't fix everything, but that can
help guide us to what people are running into. Upgrading to python2.6
allows us to clean up the syntax in our files, and makes it easier to work
on python3 compatibility.

External merge tools
********************

External merge tool configuration has been added to ``bzr`` core. The name
and commandline of one or more external merge tools can be defined in
bazaar.conf. See the help topic ``configuration`` for more details.

Tagged revisions are copied
***************************

When tags are copied from a branch, the associated revisions are now copied
too.  Previously operations like branching, merging or pulling might have
copied new tags visible in ``bzr tags``, but not copied the revisions.  Now
revisions from tags will always be present, so that operations like ``bzr
log -r tag:foo`` will always work.

Deprecated command synonyms
***************************

Two built-in synonyms for ``bzr branch`` have been deprecated: ``clone`` and
``get``.

Command options
***************

* The ``bzr log`` and ``bzr missing`` commands now accept ``-S`` as a
  shorthand for ``--short``.

Configuration files
*******************

Option values can now refer to other options in the same configuration file by
enclosing them in curly brackets (``{option}``). This is an opt-in feature
during the beta period controlled by the ``bzr.config.expand`` option that
should be declared in ``bazaar.conf`` and no other file.

Changelog merge plugin
**********************

The ``changelog_merge`` plugin has been added.  It provides a merge hook
to automate merging of changes to ``ChangeLog`` files in GNU's change log
format.  Refer to ``bzr help changelog_merge`` for documentation on how to
enable it and what it can do.

Faster operations on Large Trees
********************************

Many bzr commands used to run into pathological behavior on large trees
(>10k files), reading the inventory data in random order causing cache
thrashing (the fix was backported to bzr-2.3.2). We also updated several
code paths that were updating the WT state using an O(tree) operation to
one that was an O(changes) operation.  A possibly incomplete list is as
follows for running commands on a 70k file tree::

    bzr-2.3.1 bzr-2.3.2 bzr-2.4  action
    3m39s         1m08s   1m03s  bzr co --lightweight
      38s            8s      2s  bzr revert (in a clean tree)
    4m47s         3m56s     15s  bzr merge
    4m45s           20s      3s  bzr pull
    4m58s         3m00s      2s  bzr up
    9m33s           21s     19s  bzr uncommit (including a merge)
    4m44s           17s      2s  bzr uncommit (simple commit)
    
This is a smaller table of times for the Launchpad tree (~8k items)::

    bzr-2.3.1   bzr-2.4     action
    5.3s        5.2s        bzr co --lightweight
    0.9s        0.3s        bzr revert
    1.4s        0.4s        bzr pull
    3.9s        3.7s        bzr uncommit (with merge)
    0.9s        0.3s        bzr uncommit (without merge)

Faster stacked branches
***********************

Creating a stacked branch from a smart server with ``bzr branch
--stacked`` is a bit faster now.  For small branches it does 20% fewer
network roundtrips.  Other operations where a local branch is stacked on a
branch hosted on a smart server will also benefit.

More export control
*******************

When exporting a tree, you may now use get_export_generator() to 
do an operation after each file is exported. 

Testing
*******

The ``selftest --exclude`` option can now be specified multiple times and
the tests that match any of the specified patterns will be excluded. Only
the last specified patetrn was previously taken into account.

Digital Signature Verification
******************************

A new command ``bzr verify-signatures`` has been added to check that commits
are correctly signed with trusted keys by GPG.  This requires python-gpgme to
be installed.  ``bzr log`` has gained a ``--signatures`` option to list the
validity of signatures for each commit.  New config options ``acceptable_keys``
and ``validate_signatures_in_log`` can be set to control options to these
commands.

Further information
*******************

For more detailed information on the changes made, see the the
:doc:`../release-notes/index` for:

* the interim bzr `milestones <https://launchpad.net/bzr/2.4>`_
* the plugins you use.

For a summary of changes made in earlier releases, see:

* :doc:`whats-new-in-2.1`
* :doc:`whats-new-in-2.2`
* :doc:`whats-new-in-2.3`

..
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