1
============================
2
guidelines for modifying bzr
3
============================
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(The current version of this document is available in the file ``HACKING``
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in the source tree, or at http://doc.bazaar-vcs.org/bzr.dev/hacking.html)
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Exploring the Bazaar Platform
15
=============================
17
Before making changes, it's a good idea to explore the work already
18
done by others. Perhaps the new feature or improvement you're looking
19
for is available in another plug-in already? If you find a bug,
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perhaps someone else has already fixed it?
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To answer these questions and more, take a moment to explore the
23
overall Bazaar Platform. Here are some links to browse:
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* The Plugins page on the Wiki - http://bazaar-vcs.org/BzrPlugins
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* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
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* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
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* Blueprint Tracker for the core product - https://blueprints.launchpad.net/bzr/
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If nothing else, perhaps you'll find inspiration in how other developers
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have solved their challenges.
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Planning and Discussing Changes
38
===============================
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There is a very active community around Bazaar. Mostly we meet on IRC
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(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
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community, see http://bazaar-vcs.org/BzrSupport.
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If you are planning to make a change, it's a very good idea to mention it
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on the IRC channel and/or on the mailing list. There are many advantages
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to involving the community before you spend much time on a change.
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* you get to build on the wisdom on others, saving time
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* if others can direct you to similar code, it minimises the work to be done
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* it assists everyone in coordinating direction, priorities and effort.
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In summary, maximising the input from others typically minimises the
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total effort required to get your changes merged. The community is
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friendly, helpful and always keen to welcome newcomers.
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Bazaar Development in a Nutshell
61
================================
63
Looking for a 10 minute introduction to submitting a change?
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See http://bazaar-vcs.org/BzrGivingBack.
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TODO: Merge that Wiki page into this document.
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Understanding the Development Process
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=====================================
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The development team follows many best-practices including:
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* a public roadmap and planning process in which anyone can participate
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* time based milestones everyone can work towards and plan around
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* extensive code review and feedback to contributors
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* complete and rigorous test coverage on any code contributed
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* automated validation that all tests still pass before code is merged
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into the main code branch.
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The key tools we use to enable these practices are:
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* Launchpad - https://launchpad.net/
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* Bazaar - http://bazaar-vcs.org/
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* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
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* Patch Queue Manager - https://launchpad.net/pqm/
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For further information, see http://bazaar-vcs.org/BzrDevelopment.
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A Closer Look at the Merge & Review Process
99
===========================================
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If you'd like to propose a change, please post to the
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bazaar@lists.canonical.com list with a bundle, patch, or link to a
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branch. Put '[PATCH]' or '[MERGE]' in the subject so Bundle Buggy
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can pick it out, and explain the change in the email message text.
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Remember to update the NEWS file as part of your change if it makes any
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changes visible to users or plugin developers. Please include a diff
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against mainline if you're giving a link to a branch.
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You can generate a bundle like this::
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bzr bundle > mybundle.patch
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A .patch extension is recommended instead of .bundle as many mail clients
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will send the latter as a binary file. If a bundle would be too long or your
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mailer mangles whitespace (e.g. implicitly converts Unix newlines to DOS
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newlines), use the merge-directive command instead like this::
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bzr merge-directive http://bazaar-vcs.org http://example.org/my_branch > my_directive.patch
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See the help for details on the arguments to merge-directive.
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Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
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want it to be merged. If you want comments from developers rather than
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to be merged, you can put '[RFC]' in the subject line.
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Anyone is welcome to review code. There are broadly three gates for
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* Doesn't reduce test coverage: if it adds new methods or commands,
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there should be tests for them. There is a good test framework
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and plenty of examples to crib from, but if you are having trouble
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working out how to test something feel free to post a draft patch
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* Doesn't reduce design clarity, such as by entangling objects
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we're trying to separate. This is mostly something the more
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experienced reviewers need to help check.
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* Improves bugs, features, speed, or code simplicity.
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Code that goes in should pass all three. The core developers take care
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to keep the code quality high and understandable while recognising that
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perfect is sometimes the enemy of good. (It is easy for reviews to make
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people notice other things which should be fixed but those things should
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not hold up the original fix being accepted. New things can easily be
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recorded in the Bug Tracker instead.)
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Anyone can "vote" on the mailing list. Core developers can also vote using
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Bundle Buggy. Here are the voting codes and their explanations.
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-1 really don't want it in current form
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-0 somewhat uncomfortable
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+0 comfortable but resubmission after changes requested
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+1 conditional good to go after some minor changes
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+1 conditional is used as a way to avoid another submit/review cycle for
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patches that need small changes.
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If a change gets two +1 votes from core reviewers, and no
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vetos, then it's OK to come in. Any of the core developers can bring it
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into the bzr.dev trunk and backport it to maintenance branches if required.
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The Release Manager will merge the change into the branch for a pending
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release, if any. As a guideline, core developers usually merge their own
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changes and volunteer to merge other contributions if they were the second
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reviewer to agree to a change.
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To track the progress of proposed changes, use Bundle Buggy. See
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http://bundlebuggy.aaronbentley.com/help for a link to all the
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outstanding merge requests together with an explanation of the columns.
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Bundle Buggy will also mail you a link to track just your change.
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Preparing a Sandbox for Making Changes to Bazaar
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================================================
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Bazaar supports many ways of organising your work. See
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http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
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popular alternatives.
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Of course, the best choice for you will depend on numerous factors:
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the number of changes you may be making, the complexity of the changes, etc.
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As a starting suggestion though:
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* create a local copy of the main development branch (bzr.dev) by using
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bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
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* keep your copy of bzr.dev prestine (by not developing in it) and keep
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it up to date (by using bzr pull)
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* create a new branch off your local bzr.dev copy for each issue
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(bug or feature) you are working on.
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This approach makes it easy to go back and make any required changes
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after a code review. Resubmitting the change is then simple with no
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risk of accidentially including edits related to other issues you may
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be working on. After the changes for an issue are accepted and merged,
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the associated branch can be deleted or archived as you wish.
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Navigating the Code Base
204
========================
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TODO: List and describe in one line the purpose of each directory
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inside an installation of bzr.
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TODO: Refer to a central location holding an up to date copy of the API
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documentation generated by epydoc, e.g. something like
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http://starship.python.net/crew/mwh/bzrlibapi/bzrlib.html.
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The Importance of Testing
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=========================
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Reliability is a critical success factor for any Version Control System.
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We want Bazaar to be highly reliable across multiple platforms while
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evolving over time to meet the needs of its community.
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In a nutshell, this is want we expect and encourage:
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* New functionality should have test cases. Preferably write the
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test before writing the code.
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In general, you can test at either the command-line level or the
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internal API level. Choose whichever is appropriate: if adding a
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new command, or a new command option, then call through run_bzr().
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It is not necessary to do both.
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* Before fixing a bug, write a test case so that it does not regress.
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* Exceptions should be defined inside bzrlib.errors, so that we can
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see the whole tree at a glance.
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internal API level. See Writing Tests below for more detail.
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* Try to practice Test-Driven Development: before fixing a bug, write a
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test case so that it does not regress. Similarly for adding a new
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feature: write a test case for a small version of the new feature before
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starting on the code itself. Check the test fails on the old code, then
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add the feature or fix and check it passes.
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By doing these things, the Bazaar team gets increased confidence that
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changes do what they claim to do, whether provided by the core team or
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by community members. Equally importantly, we can be surer that changes
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down the track do not break new features or bug fixes that you are
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As of May 2007, Bazaar ships with a test suite containing over 6000 tests
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and growing. We are proud of it and want to remain so. As community
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members, we all benefit from it. Would you trust version control on
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your project to a product *without* a test suite like Bazaar has?
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Running the Test Suite
251
======================
253
Currently, bzr selftest is used to invoke tests.
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You can provide a pattern argument to run a subset. For example,
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to run just the blackbox tests, run::
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./bzr selftest -v blackbox
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To skip a particular test (or set of tests), use the --exclude option
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(shorthand -x) like so::
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./bzr selftest -v -x blackbox
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To list tests without running them, use the --list-only option like so::
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./bzr selftest --list-only
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This option can be combined with other selftest options (like -x) and
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filter patterns to understand their effect.
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In general tests should be placed in a file named test_FOO.py where
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FOO is the logical thing under test. That file should be placed in the
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tests subdirectory under the package being tested.
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For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
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See bzrlib/tests/test_sampler.py for a template test script.
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Tests can be written for the UI or for individual areas of the library.
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Choose whichever is appropriate: if adding a new command, or a new command
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option, then you should be writing a UI test. If you are both adding UI
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functionality and library functionality, you will want to write tests for
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both the UI and the core behaviours. We call UI tests 'blackbox' tests
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and they are found in ``bzrlib/tests/blackbox/*.py``.
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When writing blackbox tests please honour the following conventions:
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1. Place the tests for the command 'name' in
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bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
293
to locate the test script for a faulty command.
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2. Use the 'self.run_bzr("name")' utility function to invoke the command
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rather than running bzr in a subprocess or invoking the
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cmd_object.run() method directly. This is a lot faster than
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subprocesses and generates the same logging output as running it in a
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subprocess (which invoking the method directly does not).
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3. Only test the one command in a single test script. Use the bzrlib
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library when setting up tests and when evaluating the side-effects of
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the command. We do this so that the library api has continual pressure
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on it to be as functional as the command line in a simple manner, and
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to isolate knock-on effects throughout the blackbox test suite when a
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command changes its name or signature. Ideally only the tests for a
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given command are affected when a given command is changed.
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4. If you have a test which does actually require running bzr in a
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subprocess you can use ``run_bzr_subprocess``. By default the spawned
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process will not load plugins unless ``--allow-plugins`` is supplied.
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We make selective use of doctests__. In general they should provide
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*examples* within the API documentation which can incidentally be tested. We
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don't try to test every important case using doctests -- regular Python
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tests are generally a better solution.
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Most of these are in ``bzrlib/doc/api``. More additions are welcome.
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__ http://docs.python.org/lib/module-doctest.html
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Skipping tests and test requirements
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------------------------------------
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In our enhancements to unittest we allow for some addition results beyond
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just success or failure.
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If a test can't be run, it can say that it's skipped. This is typically
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used in parameterized tests - for example if a transport doesn't support
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setting permissions, we'll skip the tests that relating to that. ::
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return self.branch_format.initialize(repo.bzrdir)
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except errors.UninitializableFormat:
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raise tests.TestSkipped('Uninitializable branch format')
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Raising TestSkipped is a good idea when you want to make it clear that the
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test was not run, rather than just returning which makes it look as if it
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A subtly different case is a test that should run, but can't run in the
347
current environment. This covers tests that can only run in particular
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operating systems or locales, or that depend on external libraries. Here
349
we want to inform the user that they didn't get full test coverage, but
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they possibly could if they installed more libraries. These are expressed
351
as a dependency on a feature so we can summarise them, and so that the
352
test for the feature is done only once. (For historical reasons, as of
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May 2007 many cases that should depend on features currently raise
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TestSkipped.) The typical use is::
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class TestStrace(TestCaseWithTransport):
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_test_needs_features = [StraceFeature]
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which means all tests in this class need the feature. The feature itself
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should provide a ``_probe`` method which is called once to determine if
368
Known failures are when a test exists but we know it currently doesn't
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work, allowing the test suite to still pass. These should be used with
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care, we don't want a proliferation of quietly broken tests. It might be
371
appropriate to use them if you've committed a test for a bug but not the
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fix for it, or if something works on Unix but not on Windows.
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Essential Domain Classes
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########################
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Introducing the Object Model
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============================
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The core domain objects within the bazaar model are:
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Transports are explained below. See http://bazaar-vcs.org/Classes/
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for an introduction to the other key classes.
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The ``Transport`` layer handles access to local or remote directories.
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Each Transport object acts like a logical connection to a particular
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directory, and it allows various operations on files within it. You can
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*clone* a transport to get a new Transport connected to a subdirectory or
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Transports are not used for access to the working tree. At present
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working trees are always local and they are accessed through the regular
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Python file io mechanisms.
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Transports work in URLs. Take note that URLs are by definition only
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ASCII - the decision of how to encode a Unicode string into a URL must be
413
taken at a higher level, typically in the Store. (Note that Stores also
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escape filenames which cannot be safely stored on all filesystems, but
415
this is a different level.)
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The main reason for this is that it's not possible to safely roundtrip a
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URL into Unicode and then back into the same URL. The URL standard
419
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
420
doesn't say how those bytes represent non-ASCII characters. (They're not
421
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
423
For example if the user enters the url ``http://example/%e0`` there's no
424
way to tell whether that character represents "latin small letter a with
425
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
426
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
428
Equally problematic if we're given a url-like string containing non-ascii
429
characters (such as the accented a) we can't be sure how to convert that
430
to the correct URL, because we don't know what encoding the server expects
431
for those characters. (Although this is not totally reliable we might still
432
accept these and assume they should be put into UTF-8.)
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A similar edge case is that the url ``http://foo/sweet%2Fsour`` contains
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one directory component whose name is "sweet/sour". The escaped slash is
436
not a directory separator. If we try to convert URLs to regular Unicode
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paths this information will be lost.
439
This implies that Transports must natively deal with URLs; for simplicity
440
they *only* deal with URLs and conversion of other strings to URLs is done
441
elsewhere. Information they return, such as from ``list_dir``, is also in
442
the form of URL components.
451
We have a commitment to 6 months API stability - any supported symbol in a
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release of bzr MUST NOT be altered in any way that would result in
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breaking existing code that uses it. That means that method names,
454
parameter ordering, parameter names, variable and attribute names etc must
455
not be changed without leaving a 'deprecated forwarder' behind. This even
456
applies to modules and classes.
458
If you wish to change the behaviour of a supported API in an incompatible
459
way, you need to change its name as well. For instance, if I add an optional keyword
460
parameter to branch.commit - that's fine. On the other hand, if I add a
461
keyword parameter to branch.commit which is a *required* transaction
462
object, I should rename the API - i.e. to 'branch.commit_transaction'.
464
When renaming such supported API's, be sure to leave a deprecated_method (or
465
_function or ...) behind which forwards to the new API. See the
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bzrlib.symbol_versioning module for decorators that take care of the
467
details for you - such as updating the docstring, and issuing a warning
468
when the old api is used.
470
For unsupported API's, it does not hurt to follow this discipline, but it's
471
not required. Minimally though, please try to rename things so that
472
callers will at least get an AttributeError rather than weird results.
475
Coding Style Guidelines
476
=======================
478
Please write PEP-8__ compliant code.
480
One often-missed requirement is that the first line of docstrings
481
should be a self-contained one-sentence summary.
483
__ http://www.python.org/peps/pep-0008.html
18
489
* Imports should be done at the top-level of the file, unless there is
19
490
a strong reason to have them lazily loaded when a particular
20
491
function runs. Import statements have a cost, so try to make sure
21
492
they don't run inside hot functions.
23
* Please write PEP-8__ compliant code.
25
__ http://www.python.org/peps/pep-0008.html
27
494
* Module names should always be given fully-qualified,
28
495
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
501
Functions, methods or members that are in some sense "private" are given
502
a leading underscore prefix. This is just a hint that code outside the
503
implementation should probably not use that interface.
505
We prefer class names to be concatenated capital words (``TestCase``)
506
and variables, methods and functions to be lowercase words joined by
507
underscores (``revision_id``, ``get_revision``).
509
For the purposes of naming some names are treated as single compound
510
words: "filename", "revno".
512
Consider naming classes as nouns and functions/methods as verbs.
514
Try to avoid using abbreviations in names, because there can be
515
inconsistency if other people use the full name.
521
``revision_id`` not ``rev_id`` or ``revid``
523
Functions that transform one thing to another should be named ``x_to_y``
524
(not ``x2y`` as occurs in some old code.)
530
Python destructors (``__del__``) work differently to those of other
531
languages. In particular, bear in mind that destructors may be called
532
immediately when the object apparently becomes unreferenced, or at some
533
later time, or possibly never at all. Therefore we have restrictions on
534
what can be done inside them.
536
0. Never use a __del__ method without asking Martin/Robert first.
538
1. Never rely on a ``__del__`` method running. If there is code that
539
must run, do it from a ``finally`` block instead.
541
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
544
3. In some places we raise a warning from the destructor if the object
545
has not been cleaned up or closed. This is considered OK: the warning
546
may not catch every case but it's still useful sometimes.
552
In some places we have variables which point to callables that construct
553
new instances. That is to say, they can be used a lot like class objects,
554
but they shouldn't be *named* like classes:
556
> I think that things named FooBar should create instances of FooBar when
557
> called. Its plain confusing for them to do otherwise. When we have
558
> something that is going to be used as a class - that is, checked for via
559
> isinstance or other such idioms, them I would call it foo_class, so that
560
> it is clear that a callable is not sufficient. If it is only used as a
561
> factory, then yes, foo_factory is what I would use.
567
Several places in Bazaar use (or will use) a registry, which is a
568
mapping from names to objects or classes. The registry allows for
569
loading in registered code only when it's needed, and keeping
570
associated information such as a help string or description.
576
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
577
delay importing modules until they are actually used. ``lazy_import`` uses
578
the same syntax as regular python imports. So to import a few modules in a
581
from bzrlib.lazy_import import lazy_import
582
lazy_import(globals(), """
591
revision as _mod_revision,
593
import bzrlib.transport
597
At this point, all of these exist as a ``ImportReplacer`` object, ready to
598
be imported once a member is accessed. Also, when importing a module into
599
the local namespace, which is likely to clash with variable names, it is
600
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
601
the variable is a module, and these object should be hidden anyway, since
602
they shouldn't be imported into other namespaces.
605
Modules versus Members
606
~~~~~~~~~~~~~~~~~~~~~~
608
While it is possible for ``lazy_import()`` to import members of a module
609
when using the ``from module import member`` syntax, it is recommended to
610
only use that syntax to load sub modules ``from module import submodule``.
611
This is because variables and classes can frequently be used without
612
needing a sub-member for example::
614
lazy_import(globals(), """
615
from module import MyClass
619
return isinstance(x, MyClass)
621
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
622
object, rather than the real class.
625
Passing to Other Variables
626
~~~~~~~~~~~~~~~~~~~~~~~~~~
628
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
629
Because the replacer only knows about the original name, it is unable to
630
replace other variables. The ``ImportReplacer`` class will raise an
631
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
632
happened. But it requires accessing a member more than once from the new
633
variable, so some bugs are not detected right away.
35
If you change the behaviour of a command, please update its docstring
36
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
639
Processing Command Lines
640
------------------------
642
bzrlib has a standard framework for parsing command lines and calling
643
processing routines associated with various commands. See builtins.py
644
for numerous examples.
647
Standard Parameter Types
648
------------------------
650
There are some common requirements in the library: some parameters need to be
651
unicode safe, some need byte strings, and so on. At the moment we have
652
only codified one specific pattern: Parameters that need to be unicode
653
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
654
input into unicode in a consistent fashion, allowing trivial strings to be
655
used for programmer convenience, but not performing unpredictably in the
656
presence of different locales.
662
(The strategy described here is what we want to get to, but it's not
663
consistently followed in the code at the moment.)
665
bzrlib is intended to be a generically reusable library. It shouldn't
666
write messages to stdout or stderr, because some programs that use it
667
might want to display that information through a GUI or some other
670
We can distinguish two types of output from the library:
672
1. Structured data representing the progress or result of an
673
operation. For example, for a commit command this will be a list
674
of the modified files and the finally committed revision number
677
These should be exposed either through the return code or by calls
678
to a callback parameter.
680
A special case of this is progress indicators for long-lived
681
operations, where the caller should pass a ProgressBar object.
683
2. Unstructured log/debug messages, mostly for the benefit of the
684
developers or users trying to debug problems. This should always
685
be sent through ``bzrlib.trace`` and Python ``logging``, so that
686
it can be redirected by the client.
688
The distinction between the two is a bit subjective, but in general if
689
there is any chance that a library would want to see something as
690
structured data, we should make it so.
692
The policy about how output is presented in the text-mode client
693
should be only in the command-line tool.
696
Handling Errors and Exceptions
697
==============================
699
Commands should return non-zero when they encounter circumstances that
700
the user should really pay attention to - which includes trivial shell
703
Recommended values are:
706
1. Conflicts in merge-like operations, or changes are present in
707
diff-like operations.
708
2. Unrepresentable diff changes (i.e. binary files that we cannot show
710
3. An error or exception has occurred.
712
Errors are handled through Python exceptions. Exceptions should be defined
713
inside bzrlib.errors, so that we can see the whole tree at a glance.
715
We broadly classify errors as either being either internal or not,
716
depending on whether ``internal_error`` is set or not. If we think it's our
717
fault, we show a backtrace, an invitation to report the bug, and possibly
718
other details. This is the default for errors that aren't specifically
719
recognized as being caused by a user error. Otherwise we show a briefer
720
message, unless -Derror was given.
722
Many errors originate as "environmental errors" which are raised by Python
723
or builtin libraries -- for example IOError. These are treated as being
724
our fault, unless they're caught in a particular tight scope where we know
725
that they indicate a user errors. For example if the repository format
726
is not found, the user probably gave the wrong path or URL. But if one of
727
the files inside the repository is not found, then it's our fault --
728
either there's a bug in bzr, or something complicated has gone wrong in
729
the environment that means one internal file was deleted.
731
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
732
to be added near the place where they are used.
734
Exceptions are formatted for the user by conversion to a string
735
(eventually calling their ``__str__`` method.) As a convenience the
736
``._fmt`` member can be used as a template which will be mapped to the
737
error's instance dict.
739
New exception classes should be defined when callers might want to catch
740
that exception specifically, or when it needs a substantially different
743
Exception strings should start with a capital letter and should not have a
744
final fullstop. If long, they may contain newlines to break the text.
750
When you change bzrlib, please update the relevant documentation for the
751
change you made: Changes to commands should update their help, and
752
possibly end user tutorials; changes to the core library should be
753
reflected in API documentation.
38
758
If you make a user-visible change, please add a note to the NEWS file.
39
759
The description should be written to make sense to someone who's just
41
761
mentioned, but new commands, changes in behaviour or fixed nontrivial
42
762
bugs should be listed. See the existing entries for an idea of what
765
Within each release, entries in the news file should have the most
766
user-visible changes first. So the order should be approximately:
768
* changes to existing behaviour - the highest priority because the
769
user's existing knowledge is incorrect
770
* new features - should be brought to their attention
771
* bug fixes - may be of interest if the bug was affecting them, and
772
should include the bug number if any
773
* major documentation changes
774
* changes to internal interfaces
776
People who made significant contributions to each change are listed in
777
parenthesis. This can include reporting bugs (particularly with good
778
details or reproduction recipes), submitting patches, etc.
783
The docstring of a command is used by ``bzr help`` to generate help output
784
for the command. The list 'takes_options' attribute on a command is used by
785
``bzr help`` to document the options for the command - the command
786
docstring does not need to document them. Finally, the '_see_also'
787
attribute on a command can be used to reference other related help topics.
792
Functions, methods, classes and modules should have docstrings
793
describing how they are used.
795
The first line of the docstring should be a self-contained sentence.
797
For the special case of Command classes, this acts as the user-visible
798
documentation shown by the help command.
800
The docstrings should be formatted as reStructuredText_ (like this
801
document), suitable for processing using the epydoc_ tool into HTML
804
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
805
.. _epydoc: http://epydoc.sourceforge.net/
814
The copyright policy for bzr was recently made clear in this email (edited
815
for grammatical correctness)::
817
The attached patch cleans up the copyright and license statements in
818
the bzr source. It also adds tests to help us remember to add them
819
with the correct text.
821
We had the problem that lots of our files were "Copyright Canonical
822
Development Ltd" which is not a real company, and some other variations
823
on this theme. Also, some files were missing the GPL statements.
825
I want to be clear about the intent of this patch, since copyright can
826
be a little controversial.
828
1) The big motivation for this is not to shut out the community, but
829
just to clean up all of the invalid copyright statements.
831
2) It has been the general policy for bzr that we want a single
832
copyright holder for all of the core code. This is following the model
833
set by the FSF, which makes it easier to update the code to a new
834
license in case problems are encountered. (For example, if we want to
835
upgrade the project universally to GPL v3 it is much simpler if there is
836
a single copyright holder). It also makes it clearer if copyright is
837
ever debated, there is a single holder, which makes it easier to defend
838
in court, etc. (I think the FSF position is that if you assign them
839
copyright, they can defend it in court rather than you needing to, and
840
I'm sure Canonical would do the same).
841
As such, Canonical has requested copyright assignments from all of the
844
3) If someone wants to add code and not attribute it to Canonical, there
845
is a specific list of files that are excluded from this check. And the
846
test failure indicates where that is, and how to update it.
848
4) If anyone feels that I changed a copyright statement incorrectly, just
849
let me know, and I'll be happy to correct it. Whenever you have large
850
mechanical changes like this, it is possible to make some mistakes.
852
Just to reiterate, this is a community project, and it is meant to stay
853
that way. Core bzr code is copyright Canonical for legal reasons, and
854
the tests are just there to help us maintain that.
863
Bazaar has a few facilities to help debug problems by going into pdb_, the
866
.. _pdb: http://docs.python.org/lib/debugger-commands.html
868
If the ``BZR_PDB`` environment variable is set
869
then bzr will go into pdb post-mortem mode when an unhandled exception
872
If you send a SIGQUIT signal to bzr, which can be done by pressing
873
Ctrl-\\ on Unix, bzr will go into the debugger immediately. You can
874
continue execution by typing ``c``. This can be disabled if necessary
875
by setting the environment variable ``BZR_SIGQUIT_PDB=0``.
882
Integer identifier for a revision on the main line of a branch.
883
Revision 0 is always the null revision; others are 1-based
884
indexes into the branch's revision history.
887
Unicode and Encoding Support
888
============================
890
This section discusses various techniques that Bazaar uses to handle
891
characters that are outside the ASCII set.
896
When a ``Command`` object is created, it is given a member variable
897
accessible by ``self.outf``. This is a file-like object, which is bound to
898
``sys.stdout``, and should be used to write information to the screen,
899
rather than directly writing to ``sys.stdout`` or calling ``print``.
900
This file has the ability to translate Unicode objects into the correct
901
representation, based on the console encoding. Also, the class attribute
902
``encoding_type`` will effect how unprintable characters will be
903
handled. This parameter can take one of 3 values:
906
Unprintable characters will be represented with a suitable replacement
907
marker (typically '?'), and no exception will be raised. This is for
908
any command which generates text for the user to review, rather than
909
for automated processing.
910
For example: ``bzr log`` should not fail if one of the entries has text
911
that cannot be displayed.
914
Attempting to print an unprintable character will cause a UnicodeError.
915
This is for commands that are intended more as scripting support, rather
916
than plain user review.
917
For exampl: ``bzr ls`` is designed to be used with shell scripting. One
918
use would be ``bzr ls --null --unknows | xargs -0 rm``. If ``bzr``
919
printed a filename with a '?', the wrong file could be deleted. (At the
920
very least, the correct file would not be deleted). An error is used to
921
indicate that the requested action could not be performed.
924
Do not attempt to automatically convert Unicode strings. This is used
925
for commands that must handle conversion themselves.
926
For example: ``bzr diff`` needs to translate Unicode paths, but should
927
not change the exact text of the contents of the files.
930
``bzrlib.urlutils.unescape_for_display``
931
----------------------------------------
933
Because Transports work in URLs (as defined earlier), printing the raw URL
934
to the user is usually less than optimal. Characters outside the standard
935
set are printed as escapes, rather than the real character, and local
936
paths would be printed as ``file://`` urls. The function
937
``unescape_for_display`` attempts to unescape a URL, such that anything
938
that cannot be printed in the current encoding stays an escaped URL, but
939
valid characters are generated where possible.
945
The ``bzrlib.osutils`` module has many useful helper functions, including
946
some more portable variants of functions in the standard library.
948
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
949
to fail on Windows if some files are readonly or still open elsewhere.
950
Use ``bzrlib.osutils.rmtree`` instead.
956
We write some extensions in C using pyrex. We design these to work in
959
* User with no C compiler
960
* User with C compiler
963
The recommended way to install bzr is to have a C compiler so that the
964
extensions can be built, but if no C compiler is present, the pure python
965
versions we supply will work, though more slowly.
967
For developers we recommend that pyrex be installed, so that the C
968
extensions can be changed if needed.
970
For the C extensions, the extension module should always match the
971
original python one in all respects (modulo speed). This should be
972
maintained over time.
974
To create an extension, add rules to setup.py for building it with pyrex,
975
and with distutils. Now start with an empty .pyx file. At the top add
976
"include 'yourmodule.py'". This will import the contents of foo.py into this
977
file at build time - remember that only one module will be loaded at
978
runtime. Now you can subclass classes, or replace functions, and only your
979
changes need to be present in the .pyx file.
981
Note that pyrex does not support all 2.4 programming idioms, so some
982
syntax changes may be required. I.e.
984
- 'from foo import (bar, gam)' needs to change to not use the brackets.
985
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
987
If the changes are too dramatic, consider
988
maintaining the python code twice - once in the .pyx, and once in the .py,
989
and no longer including the .py file.
992
Making Installers for OS Windows
993
================================
994
To build a win32 installer, see the instructions on the wiki page:
995
http://bazaar-vcs.org/BzrWin32Installer
added
removed
doc/developers/HACKING
