1
============================
2
Guidelines for modifying bzr
3
============================
7
(The current version of this document is available in the file ``HACKING``
8
in the source tree, or at http://bazaar-ng.org/hacking.html)
13
* New functionality should have test cases. Preferably write the
14
test before writing the code.
16
In general, you can test at either the command-line level or the
17
internal API level. See Writing Tests below for more detail.
19
* Try to practice Test-Driven Development. before fixing a bug, write a
20
test case so that it does not regress. Similarly for adding a new
21
feature: write a test case for a small version of the new feature before
22
starting on the code itself. Check the test fails on the old code, then
23
add the feature or fix and check it passes.
25
* Exceptions should be defined inside bzrlib.errors, so that we can
26
see the whole tree at a glance.
28
* Imports should be done at the top-level of the file, unless there is
29
a strong reason to have them lazily loaded when a particular
30
function runs. Import statements have a cost, so try to make sure
31
they don't run inside hot functions.
33
* Module names should always be given fully-qualified,
34
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
36
* Commands should return non-zero when they encounter circumstances that
37
the user should really pay attention to - which includes trivial shell
40
Recommended values are
42
1- Conflicts in merge-like operations, or changes are present in
44
2- Unrepresentable diff changes (i.e. binary files that we cannot show
46
3- An error or exception has occurred.
51
We have a commitment to 6 months API stability - any supported symbol in a
52
release of bzr MUST NOT be altered in any way that would result in
5
This document describes the Bazaar internals and the development process.
6
It's meant for people interested in developing Bazaar, and some parts will
7
also be useful to people developing Bazaar plugins.
9
If you have any questions or something seems to be incorrect, unclear or
10
missing, please talk to us in ``irc://irc.freenode.net/#bzr``, or write to
11
the Bazaar mailing list. To propose a correction or addition to this
12
document, send a merge request or new text to the mailing list.
14
The latest developer documentation can be found online at
15
http://doc.bazaar-vcs.org/developers/.
21
Exploring the Bazaar Platform
22
=============================
24
Before making changes, it's a good idea to explore the work already
25
done by others. Perhaps the new feature or improvement you're looking
26
for is available in another plug-in already? If you find a bug,
27
perhaps someone else has already fixed it?
29
To answer these questions and more, take a moment to explore the
30
overall Bazaar Platform. Here are some links to browse:
32
* The Plugins page on the Wiki - http://bazaar-vcs.org/BzrPlugins
34
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
36
* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
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If nothing else, perhaps you'll find inspiration in how other developers
39
have solved their challenges.
41
Finding Something To Do
42
=======================
44
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
45
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
46
to the bzr log file for every method call which triggers a slow or non-scalable
47
part of the bzr library. So checking that a given command with ``-Devil`` has
48
no backtraces logged to the log file is a good way to find problem function
49
calls that might be nested deep in the code base.
51
Planning and Discussing Changes
52
===============================
54
There is a very active community around Bazaar. Mostly we meet on IRC
55
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
56
community, see http://bazaar-vcs.org/BzrSupport.
58
If you are planning to make a change, it's a very good idea to mention it
59
on the IRC channel and/or on the mailing list. There are many advantages
60
to involving the community before you spend much time on a change.
63
* you get to build on the wisdom of others, saving time
65
* if others can direct you to similar code, it minimises the work to be done
67
* it assists everyone in coordinating direction, priorities and effort.
69
In summary, maximising the input from others typically minimises the
70
total effort required to get your changes merged. The community is
71
friendly, helpful and always keen to welcome newcomers.
74
Bazaar Development in a Nutshell
75
================================
77
.. was from bazaar-vcs.org/BzrGivingBack
79
One of the fun things about working on a version control system like Bazaar is
80
that the users have a high level of proficiency in contributing back into
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the tool. Consider the following very brief introduction to contributing back
82
to Bazaar. More detailed instructions are in the following sections.
87
First, get a local copy of the development mainline (See `Why make a local
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$ bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
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Now make your own branch::
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$ bzr branch bzr.dev 123456-my-bugfix
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This will give you a branch called "123456-my-bugfix" that you can work on
100
and commit in. Here, you can study the code, make a fix or a new feature.
101
Feel free to commit early and often (after all, it's your branch!).
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Documentation improvements are an easy place to get started giving back to the
104
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
107
When you are done, make sure that you commit your last set of changes as well!
108
Once you are happy with your changes, ask for them to be merged, as described
111
Making a Merge Proposal
112
-----------------------
114
The Bazaar developers use Launchpad to further enable a truly distributed
115
style of development. Anyone can propose a branch for merging into the Bazaar
116
trunk. To start this process, you need to push your branch to Launchpad. To
117
do this, you will need a Launchpad account and user name, e.g.
118
`your_lp_username`. You can push your branch to Launchpad directly from
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$ bzr push lp:~your_lp_username/bzr/meaningful_name_here
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After you have pushed your branch, you will need to propose it for merging to
124
the Bazaar trunk. Go to
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<https://launchpad.net/your_lp_username/bzr/meaningful_name_here> and choose
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"Propose for merging into another branch". Select "~bzr/bzr/trunk" to hand
127
your changes off to the Bazaar developers for review and merging.
129
Alternatively, after pushing you can use the ``lp-propose`` command to
130
create the merge proposal.
132
Using a meaningful name for your branch will help you and the reviewer(s)
133
better track the submission. Use a very succint description of your submission
134
and prefix it with bug number if needed (lp:~mbp/bzr/484558-merge-directory
135
for example). Alternatively, you can suffix with the bug number
136
(lp:~jameinel/bzr/export-file-511987).
142
Please put a "cover letter" on your merge request explaining:
144
* the reason **why** you're making this change
146
* **how** this change achieves this purpose
148
* anything else you may have fixed in passing
150
* anything significant that you thought of doing, such as a more
151
extensive fix or a different approach, but didn't or couldn't do now
153
A good cover letter makes reviewers' lives easier because they can decide
154
from the letter whether they agree with the purpose and approach, and then
155
assess whether the patch actually does what the cover letter says.
156
Explaining any "drive-by fixes" or roads not taken may also avoid queries
157
from the reviewer. All in all this should give faster and better reviews.
158
Sometimes writing the cover letter helps the submitter realize something
159
else they need to do. The size of the cover letter should be proportional
160
to the size and complexity of the patch.
163
Why make a local copy of bzr.dev?
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---------------------------------
166
Making a local mirror of bzr.dev is not strictly necessary, but it means
168
- You can use that copy of bzr.dev as your main bzr executable, and keep it
169
up-to-date using ``bzr pull``.
170
- Certain operations are faster, and can be done when offline. For example:
173
- ``bzr diff -r ancestor:...``
176
- When it's time to create your next branch, it's more convenient. When you
177
have further contributions to make, you should do them in their own branch::
180
$ bzr branch bzr.dev additional_fixes
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$ cd additional_fixes # hack, hack, hack
185
Understanding the Development Process
186
=====================================
188
The development team follows many practices including:
190
* a public roadmap and planning process in which anyone can participate
192
* time based milestones everyone can work towards and plan around
194
* extensive code review and feedback to contributors
196
* 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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* Patch Queue Manager - https://launchpad.net/pqm/
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For further information, see <http://wiki.bazaar.canonical.com/BzrDevelopment>.
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Preparing a Sandbox for Making Changes to Bazaar
215
================================================
217
Bazaar supports many ways of organising your work. See
218
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
219
popular alternatives.
221
Of course, the best choice for you will depend on numerous factors:
222
the number of changes you may be making, the complexity of the changes, etc.
223
As a starting suggestion though:
225
* create a local copy of the main development branch (bzr.dev) by using
228
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
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* keep your copy of bzr.dev pristine (by not developing in it) and keep
231
it up to date (by using bzr pull)
233
* create a new branch off your local bzr.dev copy for each issue
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(bug or feature) you are working on.
236
This approach makes it easy to go back and make any required changes
237
after a code review. Resubmitting the change is then simple with no
238
risk of accidentally including edits related to other issues you may
239
be working on. After the changes for an issue are accepted and merged,
240
the associated branch can be deleted or archived as you wish.
243
Navigating the Code Base
244
========================
246
.. Was at <http://bazaar-vcs.org/NewDeveloperIntroduction>
248
Some of the key files in this directory are:
251
The command you run to start Bazaar itself. This script is pretty
252
short and just does some checks then jumps into bzrlib.
255
This file covers a brief introduction to Bazaar and lists some of its
259
Summary of changes in each Bazaar release that can affect users or
263
Installs Bazaar system-wide or to your home directory. To perform
264
development work on Bazaar it is not required to run this file - you
265
can simply run the bzr command from the top level directory of your
266
development copy. Note: That if you run setup.py this will create a
267
'build' directory in your development branch. There's nothing wrong
268
with this but don't be confused by it. The build process puts a copy
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of the main code base into this build directory, along with some other
270
files. You don't need to go in here for anything discussed in this
274
Possibly the most exciting folder of all, bzrlib holds the main code
275
base. This is where you will go to edit python files and contribute to
279
Holds documentation on a whole range of things on Bazaar from the
280
origination of ideas within the project to information on Bazaar
281
features and use cases. Within this directory there is a subdirectory
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for each translation into a human language. All the documentation
283
is in the ReStructuredText markup language.
286
Documentation specifically targeted at Bazaar and plugin developers.
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(Including this document.)
291
Automatically-generated API reference information is available at
292
<http://starship.python.net/crew/mwh/bzrlibapi/>.
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See also the `Bazaar Architectural Overview
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<http://doc.bazaar-vcs.org/developers/overview.html>`_.
304
We don't change APIs in stable branches: any supported symbol in a stable
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release of bzr must not be altered in any way that would result in
53
306
breaking existing code that uses it. That means that method names,
54
307
parameter ordering, parameter names, variable and attribute names etc must
55
308
not be changed without leaving a 'deprecated forwarder' behind. This even
56
309
applies to modules and classes.
58
311
If you wish to change the behaviour of a supported API in an incompatible
59
way, you need to change its name as well. For instance, if I add a optional keyword
312
way, you need to change its name as well. For instance, if I add an optional keyword
60
313
parameter to branch.commit - that's fine. On the other hand, if I add a
61
314
keyword parameter to branch.commit which is a *required* transaction
62
object, I should rename the API - i.e. to 'branch.commit_transaction'.
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object, I should rename the API - i.e. to 'branch.commit_transaction'.
317
(Actually, that may break code that provides a new implementation of
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``commit`` and doesn't expect to receive the parameter.)
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320
When renaming such supported API's, be sure to leave a deprecated_method (or
65
321
_function or ...) behind which forwards to the new API. See the
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322
bzrlib.symbol_versioning module for decorators that take care of the
67
323
details for you - such as updating the docstring, and issuing a warning
68
when the old api is used.
324
when the old API is used.
70
For unsupported API's, it does not hurt to follow this discipline, but its
326
For unsupported API's, it does not hurt to follow this discipline, but it's
71
327
not required. Minimally though, please try to rename things so that
72
328
callers will at least get an AttributeError rather than weird results.
75
Standard parameter types
331
Deprecation decorators
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----------------------
334
``bzrlib.symbol_versioning`` provides decorators that can be attached to
335
methods, functions, and other interfaces to indicate that they should no
336
longer be used. For example::
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@deprecated_method(deprecated_in((0, 1, 4)))
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return self._new_foo()
342
To deprecate a static method you must call ``deprecated_function``
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(**not** method), after the staticmethod call::
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@deprecated_function(deprecated_in((0, 1, 4)))
347
def create_repository(base, shared=False, format=None):
349
When you deprecate an API, you should not just delete its tests, because
350
then we might introduce bugs in them. If the API is still present at all,
351
it should still work. The basic approach is to use
352
``TestCase.applyDeprecated`` which in one step checks that the API gives
353
the expected deprecation message, and also returns the real result from
354
the method, so that tests can keep running.
356
Deprecation warnings will be suppressed for final releases, but not for
357
development versions or release candidates, or when running ``bzr
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selftest``. This gives developers information about whether their code is
359
using deprecated functions, but avoids confusing users about things they
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Processing Command Lines
367
------------------------
369
bzrlib has a standard framework for parsing command lines and calling
370
processing routines associated with various commands. See builtins.py
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for numerous examples.
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Standard Parameter Types
76
375
------------------------
78
377
There are some common requirements in the library: some parameters need to be
79
378
unicode safe, some need byte strings, and so on. At the moment we have
80
379
only codified one specific pattern: Parameters that need to be unicode
81
should be check via 'bzrlib.osutils.safe_unicode'. This will coerce the
380
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
82
381
input into unicode in a consistent fashion, allowing trivial strings to be
83
382
used for programmer convenience, but not performing unpredictably in the
84
383
presence of different locales.
89
If you change the behaviour of a command, please update its docstring
90
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
389
(The strategy described here is what we want to get to, but it's not
390
consistently followed in the code at the moment.)
392
bzrlib is intended to be a generically reusable library. It shouldn't
393
write messages to stdout or stderr, because some programs that use it
394
might want to display that information through a GUI or some other
397
We can distinguish two types of output from the library:
399
1. Structured data representing the progress or result of an
400
operation. For example, for a commit command this will be a list
401
of the modified files and the finally committed revision number
404
These should be exposed either through the return code or by calls
405
to a callback parameter.
407
A special case of this is progress indicators for long-lived
408
operations, where the caller should pass a ProgressBar object.
410
2. Unstructured log/debug messages, mostly for the benefit of the
411
developers or users trying to debug problems. This should always
412
be sent through ``bzrlib.trace`` and Python ``logging``, so that
413
it can be redirected by the client.
415
The distinction between the two is a bit subjective, but in general if
416
there is any chance that a library would want to see something as
417
structured data, we should make it so.
419
The policy about how output is presented in the text-mode client
420
should be only in the command-line tool.
423
Progress and Activity Indications
424
---------------------------------
426
bzrlib has a way for code to display to the user that stuff is happening
427
during a long operation. There are two particular types: *activity* which
428
means that IO is happening on a Transport, and *progress* which means that
429
higher-level application work is occurring. Both are drawn together by
432
Transport objects are responsible for calling `report_transport_activity`
435
Progress uses a model/view pattern: application code acts on a
436
`ProgressTask` object, which notifies the UI when it needs to be
437
displayed. Progress tasks form a stack. To create a new progress task on
438
top of the stack, call `bzrlib.ui.ui_factory.nested_progress_bar()`, then
439
call `update()` on the returned ProgressTask. It can be updated with just
440
a text description, with a numeric count, or with a numeric count and
441
expected total count. If an expected total count is provided the view
442
can show the progress moving along towards the expected total.
444
The user should call `finish` on the `ProgressTask` when the logical
445
operation has finished, so it can be removed from the stack.
447
Progress tasks have a complex relationship with generators: it's a very
448
good place to use them, but because python2.4 does not allow ``finally``
449
blocks in generators it's hard to clean them up properly. In this case
450
it's probably better to have the code calling the generator allocate a
451
progress task for its use and then call `finalize` when it's done, which
452
will close it if it was not already closed. The generator should also
453
finish the progress task when it exits, because it may otherwise be a long
454
time until the finally block runs.
460
When filenames or similar variables are presented inline within a message,
461
they should be enclosed in double quotes (ascii 0x22, not chiral unicode
464
bzr: ERROR: No such file "asdf"
466
When we print just a list of filenames there should not be any quoting:
469
.. _bug 544297: https://bugs.launchpad.net/bugs/544297
471
https://wiki.ubuntu.com/UnitsPolicy provides a good explanation about
472
which unit should be used when. Roughly speaking, IEC standard applies
473
for base-2 units and SI standard applies for base-10 units:
475
* for network bandwidth and disk sizes, use base-10 (Mbits/s, kB/s, GB)
477
* for RAM sizes, use base-2 (GiB, TiB)
484
Bazaar has online help for various topics through ``bzr help COMMAND`` or
485
equivalently ``bzr command -h``. We also have help on command options,
486
and on other help topics. (See ``help_topics.py``.)
488
As for python docstrings, the first paragraph should be a single-sentence
489
synopsis of the command. These are user-visible and should be prefixed with
490
``__doc__ =`` so help works under ``python -OO`` with docstrings stripped.
492
The help for options should be one or more proper sentences, starting with
493
a capital letter and finishing with a full stop (period).
495
All help messages and documentation should have two spaces between
499
Handling Errors and Exceptions
500
==============================
502
Commands should return non-zero when they encounter circumstances that
503
the user should really pay attention to - which includes trivial shell
506
Recommended values are:
509
1. Conflicts in merge-like operations, or changes are present in
510
diff-like operations.
511
2. Unrepresentable diff changes (i.e. binary files that we cannot show
513
3. An error or exception has occurred.
514
4. An internal error occurred (one that shows a traceback.)
516
Errors are handled through Python exceptions. Exceptions should be defined
517
inside bzrlib.errors, so that we can see the whole tree at a glance.
519
We broadly classify errors as either being either internal or not,
520
depending on whether ``internal_error`` is set or not. If we think it's our
521
fault, we show a backtrace, an invitation to report the bug, and possibly
522
other details. This is the default for errors that aren't specifically
523
recognized as being caused by a user error. Otherwise we show a briefer
524
message, unless -Derror was given.
526
Many errors originate as "environmental errors" which are raised by Python
527
or builtin libraries -- for example IOError. These are treated as being
528
our fault, unless they're caught in a particular tight scope where we know
529
that they indicate a user errors. For example if the repository format
530
is not found, the user probably gave the wrong path or URL. But if one of
531
the files inside the repository is not found, then it's our fault --
532
either there's a bug in bzr, or something complicated has gone wrong in
533
the environment that means one internal file was deleted.
535
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
536
to be added near the place where they are used.
538
Exceptions are formatted for the user by conversion to a string
539
(eventually calling their ``__str__`` method.) As a convenience the
540
``._fmt`` member can be used as a template which will be mapped to the
541
error's instance dict.
543
New exception classes should be defined when callers might want to catch
544
that exception specifically, or when it needs a substantially different
547
#. If it is something that a caller can recover from, a custom exception
550
#. If it is a data consistency issue, using a builtin like
551
``ValueError``/``TypeError`` is reasonable.
553
#. If it is a programmer error (using an api incorrectly)
554
``AssertionError`` is reasonable.
556
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
558
Exception strings should start with a capital letter and should not have a
559
final fullstop. If long, they may contain newlines to break the text.
566
When you change bzrlib, please update the relevant documentation for the
567
change you made: Changes to commands should update their help, and
568
possibly end user tutorials; changes to the core library should be
569
reflected in API documentation.
95
574
If you make a user-visible change, please add a note to the NEWS file.
133
624
.. _epydoc: http://epydoc.sourceforge.net/
140
Please write PEP-8__ compliant code.
142
One often-missed requirement is that the first line of docstrings
143
should be a self-contained one-sentence summary.
145
__ http://www.python.org/peps/pep-0008.html
152
Functions, methods or members that are in some sense "private" are given
153
a leading underscore prefix. This is just a hint that code outside the
154
implementation should probably not use that interface.
156
We prefer class names to be concatenated capital words (``TestCase``)
157
and variables, methods and functions to be lowercase words joined by
158
underscores (``revision_id``, ``get_revision``).
160
For the purposes of naming some names are treated as single compound
161
words: "filename", "revno".
163
Consider naming classes as nouns and functions/methods as verbs.
169
``revision_id`` not ``rev_id`` or ``revid``
171
Functions that transform one thing to another should be named ``x_to_y``
172
(not ``x2y`` as occurs in some old code.)
178
Python destructors (``__del__``) work differently to those of other
179
languages. In particular, bear in mind that destructors may be called
180
immediately when the object apparently becomes unreferenced, or at some
181
later time, or possibly never at all. Therefore we have restrictions on
182
what can be done inside them.
184
0. Never use a __del__ method without asking Martin/Robert first.
186
1. Never rely on a ``__del__`` method running. If there is code that
187
must run, do it from a ``finally`` block instead.
189
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
192
3. In some places we raise a warning from the destructor if the object
193
has not been cleaned up or closed. This is considered OK: the warning
194
may not catch every case but it's still useful sometimes.
200
(The strategy described here is what we want to get to, but it's not
201
consistently followed in the code at the moment.)
203
bzrlib is intended to be a generically reusable library. It shouldn't
204
write messages to stdout or stderr, because some programs that use it
205
might want to display that information through a GUI or some other
208
We can distinguish two types of output from the library:
210
1. Structured data representing the progress or result of an
211
operation. For example, for a commit command this will be a list
212
of the modified files and the finally committed revision number
215
These should be exposed either through the return code or by calls
216
to a callback parameter.
218
A special case of this is progress indicators for long-lived
219
operations, where the caller should pass a ProgressBar object.
221
2. Unstructured log/debug messages, mostly for the benefit of the
222
developers or users trying to debug problems. This should always
223
be sent through ``bzrlib.trace`` and Python ``logging``, so that
224
it can be redirected by the client.
226
The distinction between the two is a bit subjective, but in general if
227
there is any chance that a library would want to see something as
228
structured data, we should make it so.
230
The policy about how output is presented in the text-mode client
231
should be only in the command-line tool.
236
In general tests should be placed in a file named test_FOO.py where
237
FOO is the logical thing under test. That file should be placed in the
238
tests subdirectory under the package being tested.
240
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
241
See bzrlib/selftest/test_sampler.py for a template test script.
243
Tests can be written for the UI or for individual areas of the library.
244
Choose whichever is appropriate: if adding a new command, or a new command
245
option, then you should be writing a UI test. If you are both adding UI
246
functionality and library functionality, you will want to write tests for
247
both the UI and the core behaviours. We call UI tests 'blackbox' tests
248
and they are found in bzrlib/tests/blackbox/*.py.
250
When writing blackbox tests please honour the following conventions:
252
1. Place the tests for the command 'name' in
253
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
254
to locate the test script for a faulty command.
256
2. Use the 'self.run_bzr("name")' utility function to invoke the command
257
rather than running bzr in a subprocess or invoking the
258
cmd_object.run() method directly. This is a lot faster than
259
subprocesses and generates the same logging output as running it in a
260
subprocess (which invoking the method directly does not).
262
3. Only test the one command in a single test script. Use the bzrlib
263
library when setting up tests and when evaluating the side-effects of
264
the command. We do this so that the library api has continual pressure
265
on it to be as functional as the command line in a simple manner, and
266
to isolate knock-on effects throughout the blackbox test suite when a
267
command changes it name or signature. Ideally only the tests for a
268
given command are affected when a given command is changed.
272
Currently, bzr selftest is used to invoke tests.
273
You can provide a pattern argument to run a subset. For example,
274
to run just the blackbox tests, run::
276
./bzr selftest -v blackbox
279
Errors and exceptions
280
=====================
282
Errors are handled through Python exceptions. They can represent user
283
errors, environmental errors or program bugs. Sometimes we can't be sure
284
at the time it's raised which case applies. See bzrlib/errors.py for
285
details on the error-handling practices.
633
The copyright policy for bzr was recently made clear in this email (edited
634
for grammatical correctness)::
636
The attached patch cleans up the copyright and license statements in
637
the bzr source. It also adds tests to help us remember to add them
638
with the correct text.
640
We had the problem that lots of our files were "Copyright Canonical
641
Development Ltd" which is not a real company, and some other variations
642
on this theme. Also, some files were missing the GPL statements.
644
I want to be clear about the intent of this patch, since copyright can
645
be a little controversial.
647
1) The big motivation for this is not to shut out the community, but
648
just to clean up all of the invalid copyright statements.
650
2) It has been the general policy for bzr that we want a single
651
copyright holder for all of the core code. This is following the model
652
set by the FSF, which makes it easier to update the code to a new
653
license in case problems are encountered. (For example, if we want to
654
upgrade the project universally to GPL v3 it is much simpler if there is
655
a single copyright holder). It also makes it clearer if copyright is
656
ever debated, there is a single holder, which makes it easier to defend
657
in court, etc. (I think the FSF position is that if you assign them
658
copyright, they can defend it in court rather than you needing to, and
659
I'm sure Canonical would do the same).
660
As such, Canonical has requested copyright assignments from all of the
663
3) If someone wants to add code and not attribute it to Canonical, there
664
is a specific list of files that are excluded from this check. And the
665
test failure indicates where that is, and how to update it.
667
4) If anyone feels that I changed a copyright statement incorrectly, just
668
let me know, and I'll be happy to correct it. Whenever you have large
669
mechanical changes like this, it is possible to make some mistakes.
671
Just to reiterate, this is a community project, and it is meant to stay
672
that way. Core bzr code is copyright Canonical for legal reasons, and
673
the tests are just there to help us maintain that.
682
Bazaar has a few facilities to help debug problems by going into pdb_, the
685
.. _pdb: http://docs.python.org/lib/debugger-commands.html
687
If the ``BZR_PDB`` environment variable is set
688
then bzr will go into pdb post-mortem mode when an unhandled exception
691
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
692
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
693
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
694
this as Fn-Pause). You can continue execution by typing ``c``. This can
695
be disabled if necessary by setting the environment variable
696
``BZR_SIGQUIT_PDB=0``.
702
Bazaar accepts some global options starting with ``-D`` such as
703
``-Dhpss``. These set a value in `bzrlib.debug.debug_flags`, and
704
typically cause more information to be written to the trace file. Most
705
`mutter` calls should be guarded by a check of those flags so that we
706
don't write out too much information if it's not needed.
708
Debug flags may have effects other than just emitting trace messages.
710
Run ``bzr help global-options`` to see them all.
712
These flags may also be set as a comma-separated list in the
713
``debug_flags`` option in e.g. ``~/.bazaar/bazaar.conf``. (Note that it
714
must be in this global file, not in the branch or location configuration,
715
because it's currently only loaded at startup time.) For instance you may
716
want to always record hpss traces and to see full error tracebacks::
718
debug_flags = hpss, error
294
727
indexes into the branch's revision history.
300
If you'd like to propose a change, please post to the
301
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
302
branch. Please put '[patch]' in the subject so we can pick them out, and
303
include some text explaining the change. Remember to put an update to the NEWS
304
file in your diff, if it makes any changes visible to users or plugin
305
developers. Please include a diff against mainline if you're giving a link to
308
Please indicate if you think the code is ready to merge, or if it's just a
309
draft or for discussion. If you want comments from many developers rather than
310
to be merged, you can put '[rfc]' in the subject lines.
312
Anyone is welcome to review code. There are broadly three gates for
315
* Doesn't reduce test coverage: if it adds new methods or commands,
316
there should be tests for them. There is a good test framework
317
and plenty of examples to crib from, but if you are having trouble
318
working out how to test something feel free to post a draft patch
321
* Doesn't reduce design clarity, such as by entangling objects
322
we're trying to separate. This is mostly something the more
323
experienced reviewers need to help check.
325
* Improves bugs, features, speed, or code simplicity.
327
Code that goes in should pass all three.
329
If you read a patch please reply and say so. We can use a numeric scale
330
of -1, -0, +0, +1, meaning respectively "really don't want it in current
331
form", "somewhat uncomfortable", "ok with me", and "please put it in".
332
Anyone can "vote". (It's not really voting, just a terse expression.)
334
If something gets say two +1 votes from core reviewers, and no
335
vetos, then it's OK to come in. Any of the core developers can bring it
336
into their integration branch, which I'll merge regularly. (If you do
337
so, please reply and say so.)
730
Unicode and Encoding Support
731
============================
733
This section discusses various techniques that Bazaar uses to handle
734
characters that are outside the ASCII set.
739
When a ``Command`` object is created, it is given a member variable
740
accessible by ``self.outf``. This is a file-like object, which is bound to
741
``sys.stdout``, and should be used to write information to the screen,
742
rather than directly writing to ``sys.stdout`` or calling ``print``.
743
This file has the ability to translate Unicode objects into the correct
744
representation, based on the console encoding. Also, the class attribute
745
``encoding_type`` will effect how unprintable characters will be
746
handled. This parameter can take one of 3 values:
749
Unprintable characters will be represented with a suitable replacement
750
marker (typically '?'), and no exception will be raised. This is for
751
any command which generates text for the user to review, rather than
752
for automated processing.
753
For example: ``bzr log`` should not fail if one of the entries has text
754
that cannot be displayed.
757
Attempting to print an unprintable character will cause a UnicodeError.
758
This is for commands that are intended more as scripting support, rather
759
than plain user review.
760
For example: ``bzr ls`` is designed to be used with shell scripting. One
761
use would be ``bzr ls --null --unknowns | xargs -0 rm``. If ``bzr``
762
printed a filename with a '?', the wrong file could be deleted. (At the
763
very least, the correct file would not be deleted). An error is used to
764
indicate that the requested action could not be performed.
767
Do not attempt to automatically convert Unicode strings. This is used
768
for commands that must handle conversion themselves.
769
For example: ``bzr diff`` needs to translate Unicode paths, but should
770
not change the exact text of the contents of the files.
773
``bzrlib.urlutils.unescape_for_display``
774
----------------------------------------
776
Because Transports work in URLs (as defined earlier), printing the raw URL
777
to the user is usually less than optimal. Characters outside the standard
778
set are printed as escapes, rather than the real character, and local
779
paths would be printed as ``file://`` urls. The function
780
``unescape_for_display`` attempts to unescape a URL, such that anything
781
that cannot be printed in the current encoding stays an escaped URL, but
782
valid characters are generated where possible.
788
We write some extensions in C using pyrex. We design these to work in
791
* User with no C compiler
792
* User with C compiler
795
The recommended way to install bzr is to have a C compiler so that the
796
extensions can be built, but if no C compiler is present, the pure python
797
versions we supply will work, though more slowly.
799
For developers we recommend that pyrex be installed, so that the C
800
extensions can be changed if needed.
802
For the C extensions, the extension module should always match the
803
original python one in all respects (modulo speed). This should be
804
maintained over time.
806
To create an extension, add rules to setup.py for building it with pyrex,
807
and with distutils. Now start with an empty .pyx file. At the top add
808
"include 'yourmodule.py'". This will import the contents of foo.py into this
809
file at build time - remember that only one module will be loaded at
810
runtime. Now you can subclass classes, or replace functions, and only your
811
changes need to be present in the .pyx file.
813
Note that pyrex does not support all 2.4 programming idioms, so some
814
syntax changes may be required. I.e.
816
- 'from foo import (bar, gam)' needs to change to not use the brackets.
817
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
819
If the changes are too dramatic, consider
820
maintaining the python code twice - once in the .pyx, and once in the .py,
821
and no longer including the .py file.
824
Making Installers for OS Windows
825
================================
826
To build a win32 installer, see the instructions on the wiki page:
827
http://bazaar-vcs.org/BzrWin32Installer
836
What is a Core Developer?
837
-------------------------
839
While everyone in the Bazaar community is welcome and encouraged to
840
propose and submit changes, a smaller team is reponsible for pulling those
841
changes together into a cohesive whole. In addition to the general developer
842
stuff covered above, "core" developers have responsibility for:
845
* reviewing blueprints
847
* managing releases (see `Releasing Bazaar <http://doc.bazaar-vcs.org/developers/releasing.html>`_)
850
Removing barriers to community participation is a key reason for adopting
851
distributed VCS technology. While DVCS removes many technical barriers,
852
a small number of social barriers are often necessary instead.
853
By documenting how the above things are done, we hope to
854
encourage more people to participate in these activities, keeping the
855
differences between core and non-core contributors to a minimum.
858
Communicating and Coordinating
859
------------------------------
861
While it has many advantages, one of the challenges of distributed
862
development is keeping everyone else aware of what you're working on.
863
There are numerous ways to do this:
865
#. Assign bugs to yourself in Launchpad
866
#. Mention it on the mailing list
869
As well as the email notifcations that occur when merge requests are sent
870
and reviewed, you can keep others informed of where you're spending your
871
energy by emailing the **bazaar-commits** list implicitly. To do this,
872
install and configure the Email plugin. One way to do this is add these
873
configuration settings to your central configuration file (e.g.
874
``~/.bazaar/bazaar.conf`` on Linux)::
877
email = Joe Smith <joe.smith@internode.on.net>
878
smtp_server = mail.internode.on.net:25
880
Then add these lines for the relevant branches in ``locations.conf``::
882
post_commit_to = bazaar-commits@lists.canonical.com
883
post_commit_mailer = smtplib
885
While attending a sprint, RobertCollins' Dbus plugin is useful for the
886
same reason. See the documentation within the plugin for information on
887
how to set it up and configure it.
896
Of the many workflows supported by Bazaar, the one adopted for Bazaar
897
development itself is known as "Decentralized with automatic gatekeeper".
898
To repeat the explanation of this given on
899
http://bazaar-vcs.org/Workflows:
902
In this workflow, each developer has their own branch or
903
branches, plus read-only access to the mainline. A software gatekeeper
904
(e.g. PQM) has commit rights to the main branch. When a developer wants
905
their work merged, they request the gatekeeper to merge it. The gatekeeper
906
does a merge, a compile, and runs the test suite. If the code passes, it
907
is merged into the mainline.
909
In a nutshell, here's the overall submission process:
911
#. get your work ready (including review except for trivial changes)
912
#. push to a public location
913
#. ask PQM to merge from that location
916
At present, PQM always takes the changes to merge from a branch
917
at a URL that can be read by it. For Bazaar, that means a public,
920
As a result, the following things are needed to use PQM for submissions:
922
#. A publicly available web server
923
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
924
#. The PQM plugin installed and configured (not strictly required but
928
Selecting a Public Branch Location
929
----------------------------------
931
If you don't have your own web server running, branches can always be
932
pushed to Launchpad. Here's the process for doing that:
934
Depending on your location throughout the world and the size of your
935
repository though, it is often quicker to use an alternative public
936
location to Launchpad, particularly if you can set up your own repo and
937
push into that. By using an existing repo, push only needs to send the
938
changes, instead of the complete repository every time. Note that it is
939
easy to register branches in other locations with Launchpad so no benefits
940
are lost by going this way.
943
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
944
suggestion for public http branches. Contact your manager for information
945
on accessing this system if required.
947
It should also be noted that best practice in this area is subject to
948
change as things evolve. For example, once the Bazaar smart server on
949
Launchpad supports server-side branching, the performance situation will
950
be very different to what it is now (Jun 2007).
953
Configuring the PQM Plug-In
954
---------------------------
956
While not strictly required, the PQM plugin automates a few things and
957
reduces the chance of error. Before looking at the plugin, it helps to
958
understand a little more how PQM operates. Basically, PQM requires an
959
email indicating what you want it to do. The email typically looks like
962
star-merge source-branch target-branch
966
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
968
Note that the command needs to be on one line. The subject of the email
969
will be used for the commit message. The email also needs to be ``gpg``
970
signed with a key that PQM accepts.
972
The advantages of using the PQM plugin are:
974
#. You can use the config policies to make it easy to set up public
975
branches, so you don't have to ever type the full paths you want to merge
978
#. It checks to make sure the public branch last revision matches the
979
local last revision so you are submitting what you think you are.
981
#. It uses the same public_branch and smtp sending settings as bzr-email,
982
so if you have one set up, you have the other mostly set up.
984
#. Thunderbird refuses to not wrap lines, and request lines are usually
985
pretty long (you have 2 long URLs in there).
987
Here are sample configuration settings for the PQM plugin. Here are the
988
lines in bazaar.conf::
991
email = Joe Smith <joe.smith@internode.on.net>
992
smtp_server=mail.internode.on.net:25
994
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
995
dirstate-tags branches)::
997
[/home/joe/bzr/my-integration]
998
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
999
push_location:policy = norecurse
1000
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1001
public_branch:policy = appendpath
1002
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1003
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1005
Note that the push settings will be added by the first ``push`` on
1006
a branch. Indeed the preferred way to generate the lines above is to use
1007
``push`` with an argument, then copy-and-paste the other lines into
1014
Here is one possible recipe once the above environment is set up:
1016
#. pull bzr.dev => my-integration
1017
#. merge patch => my-integration
1018
#. fix up any final merge conflicts (NEWS being the big killer here).
1024
The ``push`` step is not required if ``my-integration`` is a checkout of
1027
Because of defaults, you can type a single message into commit and
1028
pqm-commit will reuse that.
1031
Tracking Change Acceptance
1032
--------------------------
1034
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1035
a change, you can visit this URL to confirm it was received and placed in
1038
When PQM completes processing a change, an email is sent to you with the
1049
Keeping on top of bugs reported is an important part of ongoing release
1050
planning. Everyone in the community is welcome and encouraged to raise
1051
bugs, confirm bugs raised by others, and nominate a priority. Practically
1052
though, a good percentage of bug triage is often done by the core
1053
developers, partially because of their depth of product knowledge.
1055
With respect to bug triage, core developers are encouraged to play an
1056
active role with particular attention to the following tasks:
1058
* keeping the number of unconfirmed bugs low
1059
* ensuring the priorities are generally right (everything as critical - or
1060
medium - is meaningless)
1061
* looking out for regressions and turning those around sooner rather than later.
1064
As well as prioritizing bugs and nominating them against a
1065
target milestone, Launchpad lets core developers offer to mentor others in
1070
vim: ft=rst tw=74 ai
added
removed
doc/developers/HACKING.txt
