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/
38
* Blueprint Tracker for the core product - https://blueprints.launchpad.net/bzr/
40
If nothing else, perhaps you'll find inspiration in how other developers
41
have solved their challenges.
43
Finding Something To Do
44
=======================
46
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
47
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
48
to the bzr log file for every method call which triggers a slow or non-scalable
49
part of the bzr library. So checking that a given command with ``-Devil`` has
50
no backtraces logged to the log file is a good way to find problem function
51
calls that might be nested deep in the code base.
53
Planning and Discussing Changes
54
===============================
56
There is a very active community around Bazaar. Mostly we meet on IRC
57
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
58
community, see http://bazaar-vcs.org/BzrSupport.
60
If you are planning to make a change, it's a very good idea to mention it
61
on the IRC channel and/or on the mailing list. There are many advantages
62
to involving the community before you spend much time on a change.
65
* you get to build on the wisdom of others, saving time
67
* if others can direct you to similar code, it minimises the work to be done
69
* it assists everyone in coordinating direction, priorities and effort.
71
In summary, maximising the input from others typically minimises the
72
total effort required to get your changes merged. The community is
73
friendly, helpful and always keen to welcome newcomers.
76
Bazaar Development in a Nutshell
77
================================
79
.. was from bazaar-vcs.org/BzrGivingBack
81
One of the fun things about working on a version control system like Bazaar is
82
that the users have a high level of proficiency in contributing back into
83
the tool. Consider the following very brief introduction to contributing back
84
to Bazaar. More detailed instructions are in the following sections.
89
First, get a local copy of the development mainline (See `Why make a local
95
$ bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
97
Now make your own branch::
99
$ bzr branch bzr.dev 123456-my-bugfix
101
This will give you a branch called "123456-my-bugfix" that you can work on
102
and commit in. Here, you can study the code, make a fix or a new feature.
103
Feel free to commit early and often (after all, it's your branch!).
105
Documentation improvements are an easy place to get started giving back to the
106
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
109
When you are done, make sure that you commit your last set of changes as well!
110
Once you are happy with your changes, ask for them to be merged, as described
113
Making a Merge Proposal
114
-----------------------
116
The Bazaar developers use Launchpad to further enable a truly distributed
117
style of development. Anyone can propose a branch for merging into the Bazaar
118
trunk. To start this process, you need to push your branch to Launchpad. To
119
do this, you will need a Launchpad account and user name, e.g.
120
`your_lp_username`. You can push your branch to Launchpad directly from
123
$ bzr push lp:~your_lp_username/bzr/meaningful_name_here
125
After you have pushed your branch, you will need to propose it for merging to
126
the Bazaar trunk. Go to
127
<https://launchpad.net/your_lp_username/bzr/meaningful_name_here> and choose
128
"Propose for merging into another branch". Select "~bzr/bzr/trunk" to hand
129
your changes off to the Bazaar developers for review and merging.
131
Using a meaningful name for your branch will help you and the reviewer(s)
132
better track the submission. Use a very succint description of your submission
133
and prefix it with bug number if needed (lp:~mbp/bzr/484558-merge-directory
134
for example). Alternatively, you can suffix with the bug number
135
(lp:~jameinel/bzr/export-file-511987).
138
Why make a local copy of bzr.dev?
139
---------------------------------
141
Making a local mirror of bzr.dev is not strictly necessary, but it means
143
- You can use that copy of bzr.dev as your main bzr executable, and keep it
144
up-to-date using ``bzr pull``.
145
- Certain operations are faster, and can be done when offline. For example:
148
- ``bzr diff -r ancestor:...``
151
- When it's time to create your next branch, it's more convenient. When you
152
have further contributions to make, you should do them in their own branch::
155
$ bzr branch bzr.dev additional_fixes
156
$ cd additional_fixes # hack, hack, hack
160
Understanding the Development Process
161
=====================================
163
The development team follows many practices including:
165
* a public roadmap and planning process in which anyone can participate
167
* time based milestones everyone can work towards and plan around
169
* extensive code review and feedback to contributors
171
* complete and rigorous test coverage on any code contributed
173
* automated validation that all tests still pass before code is merged
174
into the main code branch.
176
The key tools we use to enable these practices are:
178
* Launchpad - https://launchpad.net/
180
* Bazaar - http://bazaar-vcs.org/
182
* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
184
* Patch Queue Manager - https://launchpad.net/pqm/
186
For further information, see http://bazaar-vcs.org/BzrDevelopment.
191
Preparing a Sandbox for Making Changes to Bazaar
192
================================================
194
Bazaar supports many ways of organising your work. See
195
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
196
popular alternatives.
198
Of course, the best choice for you will depend on numerous factors:
199
the number of changes you may be making, the complexity of the changes, etc.
200
As a starting suggestion though:
202
* create a local copy of the main development branch (bzr.dev) by using
205
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
207
* keep your copy of bzr.dev pristine (by not developing in it) and keep
208
it up to date (by using bzr pull)
210
* create a new branch off your local bzr.dev copy for each issue
211
(bug or feature) you are working on.
213
This approach makes it easy to go back and make any required changes
214
after a code review. Resubmitting the change is then simple with no
215
risk of accidentally including edits related to other issues you may
216
be working on. After the changes for an issue are accepted and merged,
217
the associated branch can be deleted or archived as you wish.
220
Navigating the Code Base
221
========================
223
.. Was at <http://bazaar-vcs.org/NewDeveloperIntroduction>
225
Some of the key files in this directory are:
228
The command you run to start Bazaar itself. This script is pretty
229
short and just does some checks then jumps into bzrlib.
232
This file covers a brief introduction to Bazaar and lists some of its
236
Summary of changes in each Bazaar release that can affect users or
240
Installs Bazaar system-wide or to your home directory. To perform
241
development work on Bazaar it is not required to run this file - you
242
can simply run the bzr command from the top level directory of your
243
development copy. Note: That if you run setup.py this will create a
244
'build' directory in your development branch. There's nothing wrong
245
with this but don't be confused by it. The build process puts a copy
246
of the main code base into this build directory, along with some other
247
files. You don't need to go in here for anything discussed in this
251
Possibly the most exciting folder of all, bzrlib holds the main code
252
base. This is where you will go to edit python files and contribute to
256
Holds documentation on a whole range of things on Bazaar from the
257
origination of ideas within the project to information on Bazaar
258
features and use cases. Within this directory there is a subdirectory
259
for each translation into a human language. All the documentation
260
is in the ReStructuredText markup language.
263
Documentation specifically targeted at Bazaar and plugin developers.
264
(Including this document.)
268
Automatically-generated API reference information is available at
269
<http://starship.python.net/crew/mwh/bzrlibapi/>.
271
See also the `Bazaar Architectural Overview
272
<http://doc.bazaar-vcs.org/developers/overview.html>`_.
275
The Code Review Process
276
#######################
278
All code changes coming in to Bazaar are reviewed by someone else.
279
Normally changes by core contributors are reviewed by one other core
280
developer, and changes from other people are reviewed by two core
281
developers. Use intelligent discretion if the patch is trivial.
283
Good reviews do take time. They also regularly require a solid
284
understanding of the overall code base. In practice, this means a small
285
number of people often have a large review burden - with knowledge comes
286
responsibility. No one likes their merge requests sitting in a queue going
287
nowhere, so reviewing sooner rather than later is strongly encouraged.
296
Please put a "cover letter" on your merge request explaining:
298
* the reason **why** you're making this change
300
* **how** this change achieves this purpose
302
* anything else you may have fixed in passing
304
* anything significant that you thought of doing, such as a more
305
extensive fix or a different approach, but didn't or couldn't do now
307
A good cover letter makes reviewers' lives easier because they can decide
308
from the letter whether they agree with the purpose and approach, and then
309
assess whether the patch actually does what the cover letter says.
310
Explaining any "drive-by fixes" or roads not taken may also avoid queries
311
from the reviewer. All in all this should give faster and better reviews.
312
Sometimes writing the cover letter helps the submitter realize something
313
else they need to do. The size of the cover letter should be proportional
314
to the size and complexity of the patch.
317
Reviewing proposed changes
318
==========================
320
Anyone is welcome to review code, and reply to the thread with their
323
The simplest way to review a proposed change is to just read the patch on
324
the list or in Bundle Buggy. For more complex changes it may be useful
325
to make a new working tree or branch from trunk, and merge the proposed
326
change into it, so you can experiment with the code or look at a wider
329
There are three main requirements for code to get in:
331
* Doesn't reduce test coverage: if it adds new methods or commands,
332
there should be tests for them. There is a good test framework
333
and plenty of examples to crib from, but if you are having trouble
334
working out how to test something feel free to post a draft patch
337
* Doesn't reduce design clarity, such as by entangling objects
338
we're trying to separate. This is mostly something the more
339
experienced reviewers need to help check.
341
* Improves bugs, features, speed, or code simplicity.
343
Code that goes in should not degrade any of these aspects. Patches are
344
welcome that only cleanup the code without changing the external
345
behaviour. The core developers take care to keep the code quality high
346
and understandable while recognising that perfect is sometimes the enemy
349
It is easy for reviews to make people notice other things which should be
350
fixed but those things should not hold up the original fix being accepted.
351
New things can easily be recorded in the Bug Tracker instead.
353
It's normally much easier to review several smaller patches than one large
354
one. You might want to use ``bzr-loom`` to maintain threads of related
355
work, or submit a preparatory patch that will make your "real" change
359
Checklist for reviewers
360
=======================
362
* Do you understand what the code's doing and why?
364
* Will it perform reasonably for large inputs, both in memory size and
365
run time? Are there some scenarios where performance should be
368
* Is it tested, and are the tests at the right level? Are there both
369
blackbox (command-line level) and API-oriented tests?
371
* If this change will be visible to end users or API users, is it
372
appropriately documented in NEWS?
374
* Does it meet the coding standards below?
376
* If it changes the user-visible behaviour, does it update the help
377
strings and user documentation?
379
* If it adds a new major concept or standard practice, does it update the
380
developer documentation?
382
* (your ideas here...)
388
From May 2009 on, we prefer people to propose code reviews through
391
* <https://launchpad.net/+tour/code-review>
393
* <https://help.launchpad.net/Code/Review>
395
Anyone can propose or comment on a merge proposal just by creating a
398
There are two ways to create a new merge proposal: through the web
399
interface or by email.
402
Proposing a merge through the web
403
---------------------------------
405
To create the proposal through the web, first push your branch to Launchpad.
406
For example, a branch dealing with documentation belonging to the Launchpad
407
User mbp could be pushed as ::
409
bzr push lp:~mbp/bzr/doc
411
Then go to the branch's web page, which in this case would be
412
<https://code.launchpad.net/~mbp/bzr/doc>. You can simplify this step by just
417
You can then click "Propose for merging into another branch", and enter your
418
cover letter (see above) into the web form. Typically you'll want to merge
419
into ``~bzr/bzr/trunk`` which will be the default; you might also want to
420
nominate merging into a release branch for a bug fix. There is the option to
421
specify a specific reviewer or type of review, and you shouldn't normally
424
Submitting the form takes you to the new page about the merge proposal
425
containing the diff of the changes, comments by interested people, and
426
controls to comment or vote on the change.
428
Proposing a merge by mail
429
-------------------------
431
To propose a merge by mail, send a bundle to ``merge@code.launchpad.net``.
433
You can generate a merge request like this::
435
bzr send -o bug-1234.diff
437
``bzr send`` can also send mail directly if you prefer; see the help.
442
From <https://code.launchpad.net/bzr/+activereviews> you can see all
443
currently active reviews, and choose one to comment on. This page also
444
shows proposals that are now approved and should be merged by someone with
448
Reviews through Bundle Buggy
449
============================
451
The Bundle Buggy tool used up to May 2009 is still available as a review
454
Sending patches for review
455
--------------------------
457
If you'd like to propose a change, please post to the
458
bazaar@lists.canonical.com list with a bundle, patch, or link to a
459
branch. Put ``[PATCH]`` or ``[MERGE]`` in the subject so Bundle Buggy
460
can pick it out, and explain the change in the email message text.
461
Remember to update the NEWS file as part of your change if it makes any
462
changes visible to users or plugin developers. Please include a diff
463
against mainline if you're giving a link to a branch.
465
You can generate a merge request like this::
467
bzr send -o bug-1234.patch
469
A ``.patch`` extension is recommended instead of .bundle as many mail clients
470
will send the latter as a binary file.
472
``bzr send`` can also send mail directly if you prefer; see the help.
474
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
475
want it to be merged. If you want comments from developers rather than
476
to be merged, you can put ``[RFC]`` in the subject line.
478
If this change addresses a bug, please put the bug number in the subject
479
line too, in the form ``[#1]`` so that Bundle Buggy can recognize it.
481
If the change is intended for a particular release mark that in the
482
subject too, e.g. ``[1.6]``.
483
Anyone can "vote" on the mailing list by expressing an opinion. Core
484
developers can also vote using Bundle Buggy. Here are the voting codes and
487
:approve: Reviewer wants this submission merged.
488
:tweak: Reviewer wants this submission merged with small changes. (No
490
:abstain: Reviewer does not intend to vote on this patch.
491
:resubmit: Please make changes and resubmit for review.
492
:reject: Reviewer doesn't want this kind of change merged.
493
:comment: Not really a vote. Reviewer just wants to comment, for now.
495
If a change gets two approvals from core reviewers, and no rejections,
496
then it's OK to come in. Any of the core developers can bring it into the
497
bzr.dev trunk and backport it to maintenance branches if required. The
498
Release Manager will merge the change into the branch for a pending
499
release, if any. As a guideline, core developers usually merge their own
500
changes and volunteer to merge other contributions if they were the second
501
reviewer to agree to a change.
503
To track the progress of proposed changes, use Bundle Buggy. See
504
http://bundlebuggy.aaronbentley.com/help for a link to all the
505
outstanding merge requests together with an explanation of the columns.
506
Bundle Buggy will also mail you a link to track just your change.
508
Coding Style Guidelines
509
#######################
514
``hasattr`` should not be used because it swallows exceptions including
515
``KeyboardInterrupt``. Instead, say something like ::
517
if getattr(thing, 'name', None) is None
523
Please write PEP-8__ compliant code.
525
__ http://www.python.org/peps/pep-0008.html
527
One often-missed requirement is that the first line of docstrings
528
should be a self-contained one-sentence summary.
530
We use 4 space indents for blocks, and never use tab characters. (In vim,
533
Trailing white space should be avoided, but is allowed.
534
You should however not make lots of unrelated white space changes.
536
Unix style newlines (LF) are used.
538
Each file must have a newline at the end of it.
540
Lines should be no more than 79 characters if at all possible.
541
Lines that continue a long statement may be indented in either of
544
within the parenthesis or other character that opens the block, e.g.::
550
or indented by four spaces::
556
The first is considered clearer by some people; however it can be a bit
557
harder to maintain (e.g. when the method name changes), and it does not
558
work well if the relevant parenthesis is already far to the right. Avoid
561
self.legbone.kneebone.shinbone.toebone.shake_it(one,
567
self.legbone.kneebone.shinbone.toebone.shake_it(one,
573
self.legbone.kneebone.shinbone.toebone.shake_it(
576
For long lists, we like to add a trailing comma and put the closing
577
character on the following line. This makes it easier to add new items in
580
from bzrlib.goo import (
586
There should be spaces between function parameters, but not between the
587
keyword name and the value::
589
call(1, 3, cheese=quark)
593
;(defface my-invalid-face
594
; '((t (:background "Red" :underline t)))
595
; "Face used to highlight invalid constructs or other uglyties"
598
(defun my-python-mode-hook ()
599
;; setup preferred indentation style.
600
(setq fill-column 79)
601
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
602
; (font-lock-add-keywords 'python-mode
603
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
604
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
605
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
609
(add-hook 'python-mode-hook 'my-python-mode-hook)
611
The lines beginning with ';' are comments. They can be activated
612
if one want to have a strong notice of some tab/space usage
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.
619
28
* Imports should be done at the top-level of the file, unless there is
620
29
a strong reason to have them lazily loaded when a particular
624
33
* Module names should always be given fully-qualified,
625
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
53
breaking existing code that uses it. That means that method names,
54
parameter ordering, parameter names, variable and attribute names etc must
55
not be changed without leaving a 'deprecated forwarder' behind. This even
56
applies to modules and classes.
58
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
60
parameter to branch.commit - that's fine. On the other hand, if I add a
61
keyword parameter to branch.commit which is a *required* transaction
62
object, I should rename the API - i.e. to 'branch.commit_transaction'.
64
When renaming such supported API's, be sure to leave a deprecated_method (or
65
_function or ...) behind which forwards to the new API. See the
66
bzrlib.symbol_versioning module for decorators that take care of the
67
details for you - such as updating the docstring, and issuing a warning
68
when the old api is used.
70
For unsupported API's, it does not hurt to follow this discipline, but its
71
not required. Minimally though, please try to rename things so that
72
callers will at least get an AttributeError rather than weird results.
75
Standard parameter types
76
------------------------
78
There are some common requirements in the library: some parameters need to be
79
unicode safe, some need byte strings, and so on. At the moment we have
80
only codified one specific pattern: Parameters that need to be unicode
81
should be check via 'bzrlib.osutils.safe_unicode'. This will coerce the
82
input into unicode in a consistent fashion, allowing trivial strings to be
83
used for programmer convenience, but not performing unpredictably in the
84
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.
95
If you make a user-visible change, please add a note to the NEWS file.
96
The description should be written to make sense to someone who's just
97
a user of bzr, not a developer: new functions or classes shouldn't be
98
mentioned, but new commands, changes in behaviour or fixed nontrivial
99
bugs should be listed. See the existing entries for an idea of what
102
Within each release, entries in the news file should have the most
103
user-visible changes first. So the order should be approximately:
105
* changes to existing behaviour - the highest priority because the
106
user's existing knowledge is incorrect
107
* new features - should be brought to their attention
108
* bug fixes - may be of interest if the bug was affecting them, and
109
should include the bug number if any
110
* major documentation changes
111
* changes to internal interfaces
113
People who made significant contributions to each change are listed in
114
parenthesis. This can include reporting bugs (particularly with good
115
details or reproduction recipes), submitting patches, etc.
120
Functions, methods, classes and modules should have docstrings
121
describing how they are used.
123
The first line of the docstring should be a self-contained sentence.
125
For the special case of Command classes, this acts as the user-visible
126
documentation shown by the help command.
128
The docstrings should be formatted as reStructuredText_ (like this
129
document), suitable for processing using the epydoc_ tool into HTML
132
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
133
.. _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
631
Functions, methods or members that are relatively private are given
632
a leading underscore prefix. Names without a leading underscore are
633
public not just across modules but to programmers using bzrlib as an
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.
636
156
We prefer class names to be concatenated capital words (``TestCase``)
637
157
and variables, methods and functions to be lowercase words joined by
679
194
may not catch every case but it's still useful sometimes.
685
Often when something has failed later code, including cleanups invoked
686
from ``finally`` blocks, will fail too. These secondary failures are
687
generally uninteresting compared to the original exception. So use the
688
``only_raises`` decorator (from ``bzrlib.decorators``) for methods that
689
are typically called in ``finally`` blocks, such as ``unlock`` methods.
690
For example, ``@only_raises(LockNotHeld, LockBroken)``. All errors that
691
are unlikely to be a knock-on failure from a previous failure should be
698
In some places we have variables which point to callables that construct
699
new instances. That is to say, they can be used a lot like class objects,
700
but they shouldn't be *named* like classes::
702
> I think that things named FooBar should create instances of FooBar when
703
> called. Its plain confusing for them to do otherwise. When we have
704
> something that is going to be used as a class - that is, checked for via
705
> isinstance or other such idioms, them I would call it foo_class, so that
706
> it is clear that a callable is not sufficient. If it is only used as a
707
> factory, then yes, foo_factory is what I would use.
713
Several places in Bazaar use (or will use) a registry, which is a
714
mapping from names to objects or classes. The registry allows for
715
loading in registered code only when it's needed, and keeping
716
associated information such as a help string or description.
719
InterObject and multiple dispatch
720
=================================
722
The ``InterObject`` provides for two-way `multiple dispatch`__: matching
723
up for example a source and destination repository to find the right way
724
to transfer data between them.
726
.. __: http://en.wikipedia.org/wiki/Multiple_dispatch
728
There is a subclass ``InterObject`` classes for each type of object that is
729
dispatched this way, e.g. ``InterRepository``. Calling ``.get()`` on this
730
class will return an ``InterObject`` instance providing the best match for
731
those parameters, and this instance then has methods for operations
736
inter = InterRepository.get(source_repo, target_repo)
737
inter.fetch(revision_id)
739
``InterRepository`` also acts as a registry-like object for its
740
subclasses, and they can be added through ``.register_optimizer``. The
741
right one to run is selected by asking each class, in reverse order of
742
registration, whether it ``.is_compatible`` with the relevant objects.
747
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
748
delay importing modules until they are actually used. ``lazy_import`` uses
749
the same syntax as regular python imports. So to import a few modules in a
752
from bzrlib.lazy_import import lazy_import
753
lazy_import(globals(), """
762
revision as _mod_revision,
764
import bzrlib.transport
768
At this point, all of these exist as a ``ImportReplacer`` object, ready to
769
be imported once a member is accessed. Also, when importing a module into
770
the local namespace, which is likely to clash with variable names, it is
771
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
772
the variable is a module, and these object should be hidden anyway, since
773
they shouldn't be imported into other namespaces.
775
While it is possible for ``lazy_import()`` to import members of a module
776
when using the ``from module import member`` syntax, it is recommended to
777
only use that syntax to load sub modules ``from module import submodule``.
778
This is because variables and classes can frequently be used without
779
needing a sub-member for example::
781
lazy_import(globals(), """
782
from module import MyClass
786
return isinstance(x, MyClass)
788
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
789
object, rather than the real class.
791
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
792
Because the replacer only knows about the original name, it is unable to
793
replace other variables. The ``ImportReplacer`` class will raise an
794
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
795
happened. But it requires accessing a member more than once from the new
796
variable, so some bugs are not detected right away.
802
The null revision is the ancestor of all revisions. Its revno is 0, its
803
revision-id is ``null:``, and its tree is the empty tree. When referring
804
to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
805
code sometimes uses ``None`` for the null revision, but this practice is
809
Object string representations
810
=============================
812
Python prints objects using their ``__repr__`` method when they are
813
written to logs, exception tracebacks, or the debugger. We want
814
objects to have useful representations to help in determining what went
817
If you add a new class you should generally add a ``__repr__`` method
818
unless there is an adequate method in a parent class. There should be a
821
Representations should typically look like Python constructor syntax, but
822
they don't need to include every value in the object and they don't need
823
to be able to actually execute. They're to be read by humans, not
824
machines. Don't hardcode the classname in the format, so that we get the
825
correct value if the method is inherited by a subclass. If you're
826
printing attributes of the object, including strings, you should normally
827
use ``%r`` syntax (to call their repr in turn).
829
Try to avoid the representation becoming more than one or two lines long.
830
(But balance this against including useful information, and simplicity of
833
Because repr methods are often called when something has already gone
834
wrong, they should be written somewhat more defensively than most code.
835
The object may be half-initialized or in some other way in an illegal
836
state. The repr method shouldn't raise an exception, or it may hide the
837
(probably more useful) underlying exception.
842
return '%s(%r)' % (self.__class__.__name__,
849
A bare ``except`` statement will catch all exceptions, including ones that
850
really should terminate the program such as ``MemoryError`` and
851
``KeyboardInterrupt``. They should rarely be used unless the exception is
852
later re-raised. Even then, think about whether catching just
853
``Exception`` (which excludes system errors in Python2.5 and later) would
860
All code should be exercised by the test suite. See the `Bazaar Testing
861
Guide <http://doc.bazaar-vcs.org/developers/testing.html>`_ for detailed
862
information about writing tests.
871
We don't change APIs in stable branches: any supported symbol in a stable
872
release of bzr must not be altered in any way that would result in
873
breaking existing code that uses it. That means that method names,
874
parameter ordering, parameter names, variable and attribute names etc must
875
not be changed without leaving a 'deprecated forwarder' behind. This even
876
applies to modules and classes.
878
If you wish to change the behaviour of a supported API in an incompatible
879
way, you need to change its name as well. For instance, if I add an optional keyword
880
parameter to branch.commit - that's fine. On the other hand, if I add a
881
keyword parameter to branch.commit which is a *required* transaction
882
object, I should rename the API - i.e. to 'branch.commit_transaction'.
884
(Actually, that may break code that provides a new implementation of
885
``commit`` and doesn't expect to receive the parameter.)
887
When renaming such supported API's, be sure to leave a deprecated_method (or
888
_function or ...) behind which forwards to the new API. See the
889
bzrlib.symbol_versioning module for decorators that take care of the
890
details for you - such as updating the docstring, and issuing a warning
891
when the old API is used.
893
For unsupported API's, it does not hurt to follow this discipline, but it's
894
not required. Minimally though, please try to rename things so that
895
callers will at least get an AttributeError rather than weird results.
898
Deprecation decorators
899
----------------------
901
``bzrlib.symbol_versioning`` provides decorators that can be attached to
902
methods, functions, and other interfaces to indicate that they should no
903
longer be used. For example::
905
@deprecated_method(deprecated_in((0, 1, 4)))
907
return self._new_foo()
909
To deprecate a static method you must call ``deprecated_function``
910
(**not** method), after the staticmethod call::
913
@deprecated_function(deprecated_in((0, 1, 4)))
914
def create_repository(base, shared=False, format=None):
916
When you deprecate an API, you should not just delete its tests, because
917
then we might introduce bugs in them. If the API is still present at all,
918
it should still work. The basic approach is to use
919
``TestCase.applyDeprecated`` which in one step checks that the API gives
920
the expected deprecation message, and also returns the real result from
921
the method, so that tests can keep running.
923
Deprecation warnings will be suppressed for final releases, but not for
924
development versions or release candidates, or when running ``bzr
925
selftest``. This gives developers information about whether their code is
926
using deprecated functions, but avoids confusing users about things they
933
Processing Command Lines
934
------------------------
936
bzrlib has a standard framework for parsing command lines and calling
937
processing routines associated with various commands. See builtins.py
938
for numerous examples.
941
Standard Parameter Types
942
------------------------
944
There are some common requirements in the library: some parameters need to be
945
unicode safe, some need byte strings, and so on. At the moment we have
946
only codified one specific pattern: Parameters that need to be unicode
947
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
948
input into unicode in a consistent fashion, allowing trivial strings to be
949
used for programmer convenience, but not performing unpredictably in the
950
presence of different locales.
956
200
(The strategy described here is what we want to get to, but it's not
987
231
should be only in the command-line tool.
990
Progress and Activity Indications
991
---------------------------------
993
bzrlib has a way for code to display to the user that stuff is happening
994
during a long operation. There are two particular types: *activity* which
995
means that IO is happening on a Transport, and *progress* which means that
996
higher-level application work is occurring. Both are drawn together by
999
Transport objects are responsible for calling `report_transport_activity`
1002
Progress uses a model/view pattern: application code acts on a
1003
`ProgressTask` object, which notifies the UI when it needs to be
1004
displayed. Progress tasks form a stack. To create a new progress task on
1005
top of the stack, call `bzrlib.ui.ui_factory.nested_progress_bar()`, then
1006
call `update()` on the returned ProgressTask. It can be updated with just
1007
a text description, with a numeric count, or with a numeric count and
1008
expected total count. If an expected total count is provided the view
1009
can show the progress moving along towards the expected total.
1011
The user should call `finish` on the `ProgressTask` when the logical
1012
operation has finished, so it can be removed from the stack.
1014
Progress tasks have a complex relationship with generators: it's a very
1015
good place to use them, but because python2.4 does not allow ``finally``
1016
blocks in generators it's hard to clean them up properly. In this case
1017
it's probably better to have the code calling the generator allocate a
1018
progress task for its use and then call `finalize` when it's done, which
1019
will close it if it was not already closed. The generator should also
1020
finish the progress task when it exits, because it may otherwise be a long
1021
time until the finally block runs.
1023
https://wiki.ubuntu.com/UnitsPolicy provides a good explanation about
1024
which unit should be used when. Roughly speaking, IEC standard applies
1025
for base-2 units and SI standard applies for base-10 units::
1026
* for network bandwidth an disk sizes, use base-10 (Mbits/s, kB/s, GB),
1027
* for RAM sizes, use base-2 (GiB, TiB).
1033
Bazaar has online help for various topics through ``bzr help COMMAND`` or
1034
equivalently ``bzr command -h``. We also have help on command options,
1035
and on other help topics. (See ``help_topics.py``.)
1037
As for python docstrings, the first paragraph should be a single-sentence
1038
synopsis of the command.
1040
The help for options should be one or more proper sentences, starting with
1041
a capital letter and finishing with a full stop (period).
1043
All help messages and documentation should have two spaces between
1047
Handling Errors and Exceptions
1048
==============================
1050
Commands should return non-zero when they encounter circumstances that
1051
the user should really pay attention to - which includes trivial shell
1054
Recommended values are:
1057
1. Conflicts in merge-like operations, or changes are present in
1058
diff-like operations.
1059
2. Unrepresentable diff changes (i.e. binary files that we cannot show
1061
3. An error or exception has occurred.
1062
4. An internal error occurred (one that shows a traceback.)
1064
Errors are handled through Python exceptions. Exceptions should be defined
1065
inside bzrlib.errors, so that we can see the whole tree at a glance.
1067
We broadly classify errors as either being either internal or not,
1068
depending on whether ``internal_error`` is set or not. If we think it's our
1069
fault, we show a backtrace, an invitation to report the bug, and possibly
1070
other details. This is the default for errors that aren't specifically
1071
recognized as being caused by a user error. Otherwise we show a briefer
1072
message, unless -Derror was given.
1074
Many errors originate as "environmental errors" which are raised by Python
1075
or builtin libraries -- for example IOError. These are treated as being
1076
our fault, unless they're caught in a particular tight scope where we know
1077
that they indicate a user errors. For example if the repository format
1078
is not found, the user probably gave the wrong path or URL. But if one of
1079
the files inside the repository is not found, then it's our fault --
1080
either there's a bug in bzr, or something complicated has gone wrong in
1081
the environment that means one internal file was deleted.
1083
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
1084
to be added near the place where they are used.
1086
Exceptions are formatted for the user by conversion to a string
1087
(eventually calling their ``__str__`` method.) As a convenience the
1088
``._fmt`` member can be used as a template which will be mapped to the
1089
error's instance dict.
1091
New exception classes should be defined when callers might want to catch
1092
that exception specifically, or when it needs a substantially different
1095
#. If it is something that a caller can recover from, a custom exception
1098
#. If it is a data consistency issue, using a builtin like
1099
``ValueError``/``TypeError`` is reasonable.
1101
#. If it is a programmer error (using an api incorrectly)
1102
``AssertionError`` is reasonable.
1104
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
1106
Exception strings should start with a capital letter and should not have a
1107
final fullstop. If long, they may contain newlines to break the text.
1113
Do not use the Python ``assert`` statement, either in tests or elsewhere.
1114
A source test checks that it is not used. It is ok to explicitly raise
1119
* It makes the behaviour vary depending on whether bzr is run with -O
1120
or not, therefore giving a chance for bugs that occur in one case or
1121
the other, several of which have already occurred: assertions with
1122
side effects, code which can't continue unless the assertion passes,
1123
cases where we should give the user a proper message rather than an
1125
* It's not that much shorter than an explicit if/raise.
1126
* It tends to lead to fuzzy thinking about whether the check is
1127
actually needed or not, and whether it's an internal error or not
1128
* It tends to cause look-before-you-leap patterns.
1129
* It's unsafe if the check is needed to protect the integrity of the
1131
* It tends to give poor messages since the developer can get by with
1132
no explanatory text at all.
1133
* We can't rely on people always running with -O in normal use, so we
1134
can't use it for tests that are actually expensive.
1135
* Expensive checks that help developers are better turned on from the
1136
test suite or a -D flag.
1137
* If used instead of ``self.assert*()`` in tests it makes them falsely pass with -O.
1143
When you change bzrlib, please update the relevant documentation for the
1144
change you made: Changes to commands should update their help, and
1145
possibly end user tutorials; changes to the core library should be
1146
reflected in API documentation.
1151
If you make a user-visible change, please add a note to the NEWS file.
1152
The description should be written to make sense to someone who's just
1153
a user of bzr, not a developer: new functions or classes shouldn't be
1154
mentioned, but new commands, changes in behaviour or fixed nontrivial
1155
bugs should be listed. See the existing entries for an idea of what
1158
Within each release, entries in the news file should have the most
1159
user-visible changes first. So the order should be approximately:
1161
* changes to existing behaviour - the highest priority because the
1162
user's existing knowledge is incorrect
1163
* new features - should be brought to their attention
1164
* bug fixes - may be of interest if the bug was affecting them, and
1165
should include the bug number if any
1166
* major documentation changes, including fixed documentation bugs
1167
* changes to internal interfaces
1169
People who made significant contributions to each change are listed in
1170
parenthesis. This can include reporting bugs (particularly with good
1171
details or reproduction recipes), submitting patches, etc.
1173
To help with merging, NEWS entries should be sorted lexicographically
1174
within each section.
1179
The docstring of a command is used by ``bzr help`` to generate help output
1180
for the command. The list 'takes_options' attribute on a command is used by
1181
``bzr help`` to document the options for the command - the command
1182
docstring does not need to document them. Finally, the '_see_also'
1183
attribute on a command can be used to reference other related help topics.
1188
Functions, methods, classes and modules should have docstrings
1189
describing how they are used.
1191
The first line of the docstring should be a self-contained sentence.
1193
For the special case of Command classes, this acts as the user-visible
1194
documentation shown by the help command.
1196
The docstrings should be formatted as reStructuredText_ (like this
1197
document), suitable for processing using the epydoc_ tool into HTML
1200
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
1201
.. _epydoc: http://epydoc.sourceforge.net/
1210
The copyright policy for bzr was recently made clear in this email (edited
1211
for grammatical correctness)::
1213
The attached patch cleans up the copyright and license statements in
1214
the bzr source. It also adds tests to help us remember to add them
1215
with the correct text.
1217
We had the problem that lots of our files were "Copyright Canonical
1218
Development Ltd" which is not a real company, and some other variations
1219
on this theme. Also, some files were missing the GPL statements.
1221
I want to be clear about the intent of this patch, since copyright can
1222
be a little controversial.
1224
1) The big motivation for this is not to shut out the community, but
1225
just to clean up all of the invalid copyright statements.
1227
2) It has been the general policy for bzr that we want a single
1228
copyright holder for all of the core code. This is following the model
1229
set by the FSF, which makes it easier to update the code to a new
1230
license in case problems are encountered. (For example, if we want to
1231
upgrade the project universally to GPL v3 it is much simpler if there is
1232
a single copyright holder). It also makes it clearer if copyright is
1233
ever debated, there is a single holder, which makes it easier to defend
1234
in court, etc. (I think the FSF position is that if you assign them
1235
copyright, they can defend it in court rather than you needing to, and
1236
I'm sure Canonical would do the same).
1237
As such, Canonical has requested copyright assignments from all of the
1240
3) If someone wants to add code and not attribute it to Canonical, there
1241
is a specific list of files that are excluded from this check. And the
1242
test failure indicates where that is, and how to update it.
1244
4) If anyone feels that I changed a copyright statement incorrectly, just
1245
let me know, and I'll be happy to correct it. Whenever you have large
1246
mechanical changes like this, it is possible to make some mistakes.
1248
Just to reiterate, this is a community project, and it is meant to stay
1249
that way. Core bzr code is copyright Canonical for legal reasons, and
1250
the tests are just there to help us maintain that.
1253
Miscellaneous Topics
1254
####################
1259
Bazaar has a few facilities to help debug problems by going into pdb_, the
1262
.. _pdb: http://docs.python.org/lib/debugger-commands.html
1264
If the ``BZR_PDB`` environment variable is set
1265
then bzr will go into pdb post-mortem mode when an unhandled exception
1268
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
1269
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
1270
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
1271
this as Fn-Pause). You can continue execution by typing ``c``. This can
1272
be disabled if necessary by setting the environment variable
1273
``BZR_SIGQUIT_PDB=0``.
1279
Bazaar accepts some global options starting with ``-D`` such as
1280
``-Dhpss``. These set a value in `bzrlib.debug.debug_flags`, and
1281
typically cause more information to be written to the trace file. Most
1282
`mutter` calls should be guarded by a check of those flags so that we
1283
don't write out too much information if it's not needed.
1285
Debug flags may have effects other than just emitting trace messages.
1287
Run ``bzr help global-options`` to see them all.
1289
These flags may also be set as a comma-separated list in the
1290
``debug_flags`` option in e.g. ``~/.bazaar/bazaar.conf``. (Note that it
1291
must be in this global file, not in the branch or location configuration,
1292
because it's currently only loaded at startup time.) For instance you may
1293
want to always record hpss traces and to see full error tracebacks::
1295
debug_flags = hpss, error
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.
1304
294
indexes into the branch's revision history.
1307
Unicode and Encoding Support
1308
============================
1310
This section discusses various techniques that Bazaar uses to handle
1311
characters that are outside the ASCII set.
1316
When a ``Command`` object is created, it is given a member variable
1317
accessible by ``self.outf``. This is a file-like object, which is bound to
1318
``sys.stdout``, and should be used to write information to the screen,
1319
rather than directly writing to ``sys.stdout`` or calling ``print``.
1320
This file has the ability to translate Unicode objects into the correct
1321
representation, based on the console encoding. Also, the class attribute
1322
``encoding_type`` will effect how unprintable characters will be
1323
handled. This parameter can take one of 3 values:
1326
Unprintable characters will be represented with a suitable replacement
1327
marker (typically '?'), and no exception will be raised. This is for
1328
any command which generates text for the user to review, rather than
1329
for automated processing.
1330
For example: ``bzr log`` should not fail if one of the entries has text
1331
that cannot be displayed.
1334
Attempting to print an unprintable character will cause a UnicodeError.
1335
This is for commands that are intended more as scripting support, rather
1336
than plain user review.
1337
For example: ``bzr ls`` is designed to be used with shell scripting. One
1338
use would be ``bzr ls --null --unknowns | xargs -0 rm``. If ``bzr``
1339
printed a filename with a '?', the wrong file could be deleted. (At the
1340
very least, the correct file would not be deleted). An error is used to
1341
indicate that the requested action could not be performed.
1344
Do not attempt to automatically convert Unicode strings. This is used
1345
for commands that must handle conversion themselves.
1346
For example: ``bzr diff`` needs to translate Unicode paths, but should
1347
not change the exact text of the contents of the files.
1350
``bzrlib.urlutils.unescape_for_display``
1351
----------------------------------------
1353
Because Transports work in URLs (as defined earlier), printing the raw URL
1354
to the user is usually less than optimal. Characters outside the standard
1355
set are printed as escapes, rather than the real character, and local
1356
paths would be printed as ``file://`` urls. The function
1357
``unescape_for_display`` attempts to unescape a URL, such that anything
1358
that cannot be printed in the current encoding stays an escaped URL, but
1359
valid characters are generated where possible.
1365
The ``bzrlib.osutils`` module has many useful helper functions, including
1366
some more portable variants of functions in the standard library.
1368
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
1369
to fail on Windows if some files are readonly or still open elsewhere.
1370
Use ``bzrlib.osutils.rmtree`` instead.
1376
We write some extensions in C using pyrex. We design these to work in
1379
* User with no C compiler
1380
* User with C compiler
1383
The recommended way to install bzr is to have a C compiler so that the
1384
extensions can be built, but if no C compiler is present, the pure python
1385
versions we supply will work, though more slowly.
1387
For developers we recommend that pyrex be installed, so that the C
1388
extensions can be changed if needed.
1390
For the C extensions, the extension module should always match the
1391
original python one in all respects (modulo speed). This should be
1392
maintained over time.
1394
To create an extension, add rules to setup.py for building it with pyrex,
1395
and with distutils. Now start with an empty .pyx file. At the top add
1396
"include 'yourmodule.py'". This will import the contents of foo.py into this
1397
file at build time - remember that only one module will be loaded at
1398
runtime. Now you can subclass classes, or replace functions, and only your
1399
changes need to be present in the .pyx file.
1401
Note that pyrex does not support all 2.4 programming idioms, so some
1402
syntax changes may be required. I.e.
1404
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1405
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1407
If the changes are too dramatic, consider
1408
maintaining the python code twice - once in the .pyx, and once in the .py,
1409
and no longer including the .py file.
1412
Making Installers for OS Windows
1413
================================
1414
To build a win32 installer, see the instructions on the wiki page:
1415
http://bazaar-vcs.org/BzrWin32Installer
1418
Core Developer Tasks
1419
####################
1424
What is a Core Developer?
1425
-------------------------
1427
While everyone in the Bazaar community is welcome and encouraged to
1428
propose and submit changes, a smaller team is reponsible for pulling those
1429
changes together into a cohesive whole. In addition to the general developer
1430
stuff covered above, "core" developers have responsibility for:
1433
* reviewing blueprints
1435
* managing releases (see `Releasing Bazaar <http://doc.bazaar-vcs.org/developers/releasing.html>`_)
1438
Removing barriers to community participation is a key reason for adopting
1439
distributed VCS technology. While DVCS removes many technical barriers,
1440
a small number of social barriers are often necessary instead.
1441
By documenting how the above things are done, we hope to
1442
encourage more people to participate in these activities, keeping the
1443
differences between core and non-core contributors to a minimum.
1446
Communicating and Coordinating
1447
------------------------------
1449
While it has many advantages, one of the challenges of distributed
1450
development is keeping everyone else aware of what you're working on.
1451
There are numerous ways to do this:
1453
#. Assign bugs to yourself in Launchpad
1454
#. Mention it on the mailing list
1455
#. Mention it on IRC
1457
As well as the email notifcations that occur when merge requests are sent
1458
and reviewed, you can keep others informed of where you're spending your
1459
energy by emailing the **bazaar-commits** list implicitly. To do this,
1460
install and configure the Email plugin. One way to do this is add these
1461
configuration settings to your central configuration file (e.g.
1462
``~/.bazaar/bazaar.conf`` on Linux)::
1465
email = Joe Smith <joe.smith@internode.on.net>
1466
smtp_server = mail.internode.on.net:25
1468
Then add these lines for the relevant branches in ``locations.conf``::
1470
post_commit_to = bazaar-commits@lists.canonical.com
1471
post_commit_mailer = smtplib
1473
While attending a sprint, RobertCollins' Dbus plugin is useful for the
1474
same reason. See the documentation within the plugin for information on
1475
how to set it up and configure it.
1484
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1485
development itself is known as "Decentralized with automatic gatekeeper".
1486
To repeat the explanation of this given on
1487
http://bazaar-vcs.org/Workflows:
1490
In this workflow, each developer has their own branch or
1491
branches, plus read-only access to the mainline. A software gatekeeper
1492
(e.g. PQM) has commit rights to the main branch. When a developer wants
1493
their work merged, they request the gatekeeper to merge it. The gatekeeper
1494
does a merge, a compile, and runs the test suite. If the code passes, it
1495
is merged into the mainline.
1497
In a nutshell, here's the overall submission process:
1499
#. get your work ready (including review except for trivial changes)
1500
#. push to a public location
1501
#. ask PQM to merge from that location
1504
At present, PQM always takes the changes to merge from a branch
1505
at a URL that can be read by it. For Bazaar, that means a public,
1506
typically http, URL.
1508
As a result, the following things are needed to use PQM for submissions:
1510
#. A publicly available web server
1511
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1512
#. The PQM plugin installed and configured (not strictly required but
1513
highly recommended).
1516
Selecting a Public Branch Location
1517
----------------------------------
1519
If you don't have your own web server running, branches can always be
1520
pushed to Launchpad. Here's the process for doing that:
1522
Depending on your location throughout the world and the size of your
1523
repository though, it is often quicker to use an alternative public
1524
location to Launchpad, particularly if you can set up your own repo and
1525
push into that. By using an existing repo, push only needs to send the
1526
changes, instead of the complete repository every time. Note that it is
1527
easy to register branches in other locations with Launchpad so no benefits
1528
are lost by going this way.
1531
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1532
suggestion for public http branches. Contact your manager for information
1533
on accessing this system if required.
1535
It should also be noted that best practice in this area is subject to
1536
change as things evolve. For example, once the Bazaar smart server on
1537
Launchpad supports server-side branching, the performance situation will
1538
be very different to what it is now (Jun 2007).
1541
Configuring the PQM Plug-In
1542
---------------------------
1544
While not strictly required, the PQM plugin automates a few things and
1545
reduces the chance of error. Before looking at the plugin, it helps to
1546
understand a little more how PQM operates. Basically, PQM requires an
1547
email indicating what you want it to do. The email typically looks like
1550
star-merge source-branch target-branch
1554
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1556
Note that the command needs to be on one line. The subject of the email
1557
will be used for the commit message. The email also needs to be ``gpg``
1558
signed with a key that PQM accepts.
1560
The advantages of using the PQM plugin are:
1562
#. You can use the config policies to make it easy to set up public
1563
branches, so you don't have to ever type the full paths you want to merge
1566
#. It checks to make sure the public branch last revision matches the
1567
local last revision so you are submitting what you think you are.
1569
#. It uses the same public_branch and smtp sending settings as bzr-email,
1570
so if you have one set up, you have the other mostly set up.
1572
#. Thunderbird refuses to not wrap lines, and request lines are usually
1573
pretty long (you have 2 long URLs in there).
1575
Here are sample configuration settings for the PQM plugin. Here are the
1576
lines in bazaar.conf::
1579
email = Joe Smith <joe.smith@internode.on.net>
1580
smtp_server=mail.internode.on.net:25
1582
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1583
dirstate-tags branches)::
1585
[/home/joe/bzr/my-integration]
1586
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1587
push_location:policy = norecurse
1588
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1589
public_branch:policy = appendpath
1590
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1591
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1593
Note that the push settings will be added by the first ``push`` on
1594
a branch. Indeed the preferred way to generate the lines above is to use
1595
``push`` with an argument, then copy-and-paste the other lines into
1602
Here is one possible recipe once the above environment is set up:
1604
#. pull bzr.dev => my-integration
1605
#. merge patch => my-integration
1606
#. fix up any final merge conflicts (NEWS being the big killer here).
1612
The ``push`` step is not required if ``my-integration`` is a checkout of
1615
Because of defaults, you can type a single message into commit and
1616
pqm-commit will reuse that.
1619
Tracking Change Acceptance
1620
--------------------------
1622
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1623
a change, you can visit this URL to confirm it was received and placed in
1626
When PQM completes processing a change, an email is sent to you with the
1630
Reviewing Blueprints
300
The ``Transport`` layer handles access to local or remote directories.
301
Each Transport object acts like a logical connection to a particular
302
directory, and it allows various operations on files within it. You can
303
*clone* a transport to get a new Transport connected to a subdirectory or
306
Transports are not used for access to the working tree. At present
307
working trees are always local and they are accessed through the regular
308
Python file io mechanisms.
313
Transports work in URLs. Take note that URLs are by definition only
314
ASCII - the decision of how to encode a Unicode string into a URL must be
315
taken at a higher level, typically in the Store. (Note that Stores also
316
escape filenames which cannot be safely stored on all filesystems, but
317
this is a different level.)
319
The main reason for this is that it's not possible to safely roundtrip a
320
URL into Unicode and then back into the same URL. The URL standard
321
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
322
doesn't say how those bytes represent non-ASCII characters. (They're not
323
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
325
For example if the user enters the url ``http://example/%e0`` there's no
326
way to tell whether that character represents "latin small letter a with
327
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
328
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
330
Equally problematic if we're given a url-like string containing non-ascii
331
characters (such as the accented a) we can't be sure how to convert that
332
to the correct URL, because we don't know what encoding the server expects
333
for those characters. (Although this is not totally reliable we might still
334
accept these and assume they should be put into UTF-8.)
336
A similar edge case is that the url ``http://foo/sweet%2Fsour" contains
337
one directory component whose name is "sweet/sour". The escaped slash is
338
not a directory separator. If we try to convert URLs to regular Unicode
339
paths this information will be lost.
341
This implies that Transports must natively deal with URLs; for simplicity
342
they *only* deal with URLs and conversion of other strings to URLs is done
343
elsewhere. Information they return, such as from ``list_dir``, is also in
344
the form of URL components.
1631
348
====================
1633
Blueprint Tracking Using Launchpad
1634
----------------------------------
1636
New features typically require a fair amount of discussion, design and
1637
debate. For Bazaar, that information is often captured in a so-called
1638
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1639
is done using Launchpad's relevant tracker,
1640
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1641
review, please announce it on the mailing list.
1643
Alternatively, send an email beginning with [RFC] with the proposal to the
1644
list. In some cases, you may wish to attach proposed code or a proposed
1645
developer document if that best communicates the idea. Debate can then
1646
proceed using the normal merge review processes.
1649
Recording Blueprint Review Feedback
1650
-----------------------------------
1652
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1653
(Jun 2007) support a chronological list of comment responses. Review
1654
feedback can either be recorded on the Wiki hosting the blueprints or by
1655
using Launchpad's whiteboard feature.
1662
Using Releases and Milestones in Launchpad
1663
------------------------------------------
1665
TODO ... (Exact policies still under discussion)
1671
Keeping on top of bugs reported is an important part of ongoing release
1672
planning. Everyone in the community is welcome and encouraged to raise
1673
bugs, confirm bugs raised by others, and nominate a priority. Practically
1674
though, a good percentage of bug triage is often done by the core
1675
developers, partially because of their depth of product knowledge.
1677
With respect to bug triage, core developers are encouraged to play an
1678
active role with particular attention to the following tasks:
1680
* keeping the number of unconfirmed bugs low
1681
* ensuring the priorities are generally right (everything as critical - or
1682
medium - is meaningless)
1683
* looking out for regressions and turning those around sooner rather than later.
1686
As well as prioritizing bugs and nominating them against a
1687
target milestone, Launchpad lets core developers offer to mentor others in
1692
vim: ft=rst tw=74 ai
350
If you'd like to propose a change, please post to the
351
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
352
branch. Please put '[patch]' in the subject so we can pick them out, and
353
include some text explaining the change. Remember to put an update to the NEWS
354
file in your diff, if it makes any changes visible to users or plugin
355
developers. Please include a diff against mainline if you're giving a link to
358
Please indicate if you think the code is ready to merge, or if it's just a
359
draft or for discussion. If you want comments from many developers rather than
360
to be merged, you can put '[rfc]' in the subject lines.
362
Anyone is welcome to review code. There are broadly three gates for
365
* Doesn't reduce test coverage: if it adds new methods or commands,
366
there should be tests for them. There is a good test framework
367
and plenty of examples to crib from, but if you are having trouble
368
working out how to test something feel free to post a draft patch
371
* Doesn't reduce design clarity, such as by entangling objects
372
we're trying to separate. This is mostly something the more
373
experienced reviewers need to help check.
375
* Improves bugs, features, speed, or code simplicity.
377
Code that goes in should pass all three.
379
If you read a patch please reply and say so. We can use a numeric scale
380
of -1, -0, +0, +1, meaning respectively "really don't want it in current
381
form", "somewhat uncomfortable", "ok with me", and "please put it in".
382
Anyone can "vote". (It's not really voting, just a terse expression.)
384
If something gets say two +1 votes from core reviewers, and no
385
vetos, then it's OK to come in. Any of the core developers can bring it
386
into their integration branch, which I'll merge regularly. (If you do
387
so, please reply and say so.)
added
removed
HACKING
