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 current version of this document is available in the file
15
``doc/en/developer-guide/HACKING.txt`` in the source tree, or at
16
http://doc.bazaar-vcs.org/bzr.dev/en/developer-guide/HACKING.html
19
`Bazaar Developer Documentation Catalog <../../developers/index.html>`_.
1
============================
2
Guidelines for modifying bzr
3
============================
27
Exploring the Bazaar Platform
28
=============================
30
Before making changes, it's a good idea to explore the work already
31
done by others. Perhaps the new feature or improvement you're looking
32
for is available in another plug-in already? If you find a bug,
33
perhaps someone else has already fixed it?
35
To answer these questions and more, take a moment to explore the
36
overall Bazaar Platform. Here are some links to browse:
38
* The Plugins page on the Wiki - http://bazaar-vcs.org/BzrPlugins
40
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
42
* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
44
* Blueprint Tracker for the core product - https://blueprints.launchpad.net/bzr/
46
If nothing else, perhaps you'll find inspiration in how other developers
47
have solved their challenges.
49
Finding Something To Do
50
=======================
52
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
53
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
54
to the bzr log file for every method call which triggers a slow or non-scalable
55
part of the bzr library. So checking that a given command with ``-Devil`` has
56
no backtraces logged to the log file is a good way to find problem function
57
calls that might be nested deep in the code base.
59
Planning and Discussing Changes
60
===============================
62
There is a very active community around Bazaar. Mostly we meet on IRC
63
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
64
community, see http://bazaar-vcs.org/BzrSupport.
66
If you are planning to make a change, it's a very good idea to mention it
67
on the IRC channel and/or on the mailing list. There are many advantages
68
to involving the community before you spend much time on a change.
71
* you get to build on the wisdom on others, saving time
73
* if others can direct you to similar code, it minimises the work to be done
75
* it assists everyone in coordinating direction, priorities and effort.
77
In summary, maximising the input from others typically minimises the
78
total effort required to get your changes merged. The community is
79
friendly, helpful and always keen to welcome newcomers.
82
Bazaar Development in a Nutshell
83
================================
85
.. was from bazaar-vcs.org/BzrGivingBack
87
One of the fun things about working on a version control system like Bazaar is
88
that the users have a high level of proficiency in contributing back into
89
the tool. Consider the following very brief introduction to contributing back
90
to Bazaar. More detailed instructions are in the following sections.
95
First, get a local copy of the development mainline (See `Why make a local
101
$ bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
103
Now make your own branch::
105
$ bzr branch bzr.dev 123456-my-bugfix
107
This will give you a branch called "123456-my-bugfix" that you can work on
108
and commit in. Here, you can study the code, make a fix or a new feature.
109
Feel free to commit early and often (after all, it's your branch!).
111
Documentation improvements are an easy place to get started giving back to the
112
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
115
When you are done, make sure that you commit your last set of changes as well!
116
Once you are happy with your changes, ask for them to be merged, as described
119
Making a Merge Proposal
120
-----------------------
122
The Bazaar developers use Launchpad to further enable a truly distributed
123
style of development. Anyone can propose a branch for merging into the Bazaar
124
trunk. To start this process, you need to push your branch to Launchpad. To
125
do this, you will need a Launchpad account and user name, e.g.
126
`your_lp_username`. You can push your branch to Launchpad directly from
129
$ bzr push lp:~your_lp_username/bzr/giveback
131
After you have pushed your branch, you will need to propose it for merging to
132
the Bazaar trunk. Go to <https://launchpad.net/your_lp_username/bzr/giveback>
133
and choose "Propose for merging into another branch". Select "~bzr/bzr/trunk"
134
to hand your changes off to the Bazaar developers for review and merging.
136
Why make a local copy of bzr.dev?
137
---------------------------------
139
Making a local mirror of bzr.dev is not strictly necessary, but it means
141
- You can use that copy of bzr.dev as your main bzr executable, and keep it
142
up-to-date using ``bzr pull``.
143
- Certain operations are faster, and can be done when offline. For example:
146
- ``bzr diff -r ancestor:...``
149
- When it's time to create your next branch, it's more convenient. When you
150
have further contributions to make, you should do them in their own branch::
153
$ bzr branch bzr.dev additional_fixes
154
$ cd additional_fixes # hack, hack, hack
158
Understanding the Development Process
159
=====================================
161
The development team follows many practices including:
163
* a public roadmap and planning process in which anyone can participate
165
* time based milestones everyone can work towards and plan around
167
* extensive code review and feedback to contributors
169
* complete and rigorous test coverage on any code contributed
171
* automated validation that all tests still pass before code is merged
172
into the main code branch.
174
The key tools we use to enable these practices are:
176
* Launchpad - https://launchpad.net/
178
* Bazaar - http://bazaar-vcs.org/
180
* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
182
* Patch Queue Manager - https://launchpad.net/pqm/
184
For further information, see http://bazaar-vcs.org/BzrDevelopment.
189
Preparing a Sandbox for Making Changes to Bazaar
190
================================================
192
Bazaar supports many ways of organising your work. See
193
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
194
popular alternatives.
196
Of course, the best choice for you will depend on numerous factors:
197
the number of changes you may be making, the complexity of the changes, etc.
198
As a starting suggestion though:
200
* create a local copy of the main development branch (bzr.dev) by using
203
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
205
* keep your copy of bzr.dev pristine (by not developing in it) and keep
206
it up to date (by using bzr pull)
208
* create a new branch off your local bzr.dev copy for each issue
209
(bug or feature) you are working on.
211
This approach makes it easy to go back and make any required changes
212
after a code review. Resubmitting the change is then simple with no
213
risk of accidentally including edits related to other issues you may
214
be working on. After the changes for an issue are accepted and merged,
215
the associated branch can be deleted or archived as you wish.
218
Navigating the Code Base
219
========================
221
.. Was at <http://bazaar-vcs.org/NewDeveloperIntroduction>
223
Some of the key files in this directory are:
226
The command you run to start Bazaar itself. This script is pretty
227
short and just does some checks then jumps into bzrlib.
230
This file covers a brief introduction to Bazaar and lists some of its
234
Summary of changes in each Bazaar release that can affect users or
238
Installs Bazaar system-wide or to your home directory. To perform
239
development work on Bazaar it is not required to run this file - you
240
can simply run the bzr command from the top level directory of your
241
development copy. Note: That if you run setup.py this will create a
242
'build' directory in your development branch. There's nothing wrong
243
with this but don't be confused by it. The build process puts a copy
244
of the main code base into this build directory, along with some other
245
files. You don't need to go in here for anything discussed in this
249
Possibly the most exciting folder of all, bzrlib holds the main code
250
base. This is where you will go to edit python files and contribute to
254
Holds documentation on a whole range of things on Bazaar from the
255
origination of ideas within the project to information on Bazaar
256
features and use cases. Within this directory there is a subdirectory
257
for each translation into a human language. All the documentation
258
is in the ReStructuredText markup language.
261
Documentation specifically targeted at Bazaar and plugin developers.
262
(Including this document.)
266
Automatically-generated API reference information is available at
267
<http://starship.python.net/crew/mwh/bzrlibapi/>.
269
See also the `Bazaar Architectural Overview <../../developers/overview.html>`_.
272
The Code Review Process
273
#######################
275
All code changes coming in to Bazaar are reviewed by someone else.
276
Normally changes by core contributors are reviewed by one other core
277
developer, and changes from other people are reviewed by two core
278
developers. Use intelligent discretion if the patch is trivial.
280
Good reviews do take time. They also regularly require a solid
281
understanding of the overall code base. In practice, this means a small
282
number of people often have a large review burden - with knowledge comes
283
responsibility. No one likes their merge requests sitting in a queue going
284
nowhere, so reviewing sooner rather than later is strongly encouraged.
293
Please put a "cover letter" on your merge request explaining:
295
* the reason **why** you're making this change
297
* **how** this change achieves this purpose
299
* anything else you may have fixed in passing
301
* anything significant that you thought of doing, such as a more
302
extensive fix or a different approach, but didn't or couldn't do now
304
A good cover letter makes reviewers' lives easier because they can decide
305
from the letter whether they agree with the purpose and approach, and then
306
assess whether the patch actually does what the cover letter says.
307
Explaining any "drive-by fixes" or roads not taken may also avoid queries
308
from the reviewer. All in all this should give faster and better reviews.
309
Sometimes writing the cover letter helps the submitter realize something
310
else they need to do. The size of the cover letter should be proportional
311
to the size and complexity of the patch.
314
Reviewing proposed changes
315
==========================
317
Anyone is welcome to review code, and reply to the thread with their
320
The simplest way to review a proposed change is to just read the patch on
321
the list or in Bundle Buggy. For more complex changes it may be useful
322
to make a new working tree or branch from trunk, and merge the proposed
323
change into it, so you can experiment with the code or look at a wider
326
There are three main requirements for code to get in:
328
* Doesn't reduce test coverage: if it adds new methods or commands,
329
there should be tests for them. There is a good test framework
330
and plenty of examples to crib from, but if you are having trouble
331
working out how to test something feel free to post a draft patch
334
* Doesn't reduce design clarity, such as by entangling objects
335
we're trying to separate. This is mostly something the more
336
experienced reviewers need to help check.
338
* Improves bugs, features, speed, or code simplicity.
340
Code that goes in should not degrade any of these aspects. Patches are
341
welcome that only cleanup the code without changing the external
342
behaviour. The core developers take care to keep the code quality high
343
and understandable while recognising that perfect is sometimes the enemy
346
It is easy for reviews to make people notice other things which should be
347
fixed but those things should not hold up the original fix being accepted.
348
New things can easily be recorded in the Bug Tracker instead.
350
It's normally much easier to review several smaller patches than one large
351
one. You might want to use ``bzr-loom`` to maintain threads of related
352
work, or submit a preparatory patch that will make your "real" change
356
Checklist for reviewers
357
=======================
359
* Do you understand what the code's doing and why?
361
* Will it perform reasonably for large inputs, both in memory size and
362
run time? Are there some scenarios where performance should be
365
* Is it tested, and are the tests at the right level? Are there both
366
blackbox (command-line level) and API-oriented tests?
368
* If this change will be visible to end users or API users, is it
369
appropriately documented in NEWS?
371
* Does it meet the coding standards below?
373
* If it changes the user-visible behaviour, does it update the help
374
strings and user documentation?
376
* If it adds a new major concept or standard practice, does it update the
377
developer documentation?
379
* (your ideas here...)
385
From May 2009 on, we prefer people to propose code reviews through
388
* <https://launchpad.net/+tour/code-review>
390
* <https://help.launchpad.net/Code/Review>
392
Anyone can propose or comment on a merge proposal just by creating a
395
There are two ways to create a new merge proposal: through the web
396
interface or by email.
399
Proposing a merge through the web
400
---------------------------------
402
To create the proposal through the web, first push your branch to Launchpad.
403
For example, a branch dealing with documentation belonging to the Launchpad
404
User mbp could be pushed as ::
406
bzr push lp:~mbp/bzr/doc
408
Then go to the branch's web page, which in this case would be
409
<https://code.launchpad.net/~mbp/bzr/doc>. You can simplify this step by just
414
You can then click "Propose for merging into another branch", and enter your
415
cover letter (see above) into the web form. Typically you'll want to merge
416
into ``~bzr/bzr/trunk`` which will be the default; you might also want to
417
nominate merging into a release branch for a bug fix. There is the option to
418
specify a specific reviewer or type of review, and you shouldn't normally
421
Submitting the form takes you to the new page about the merge proposal
422
containing the diff of the changes, comments by interested people, and
423
controls to comment or vote on the change.
425
Proposing a merge by mail
426
-------------------------
428
To propose a merge by mail, send a bundle to ``merge@code.launchpad.net``.
430
You can generate a merge request like this::
432
bzr send -o bug-1234.diff
434
``bzr send`` can also send mail directly if you prefer; see the help.
439
From <https://code.launchpad.net/bzr/+activereviews> you can see all
440
currently active reviews, and choose one to comment on. This page also
441
shows proposals that are now approved and should be merged by someone with
445
Reviews through Bundle Buggy
446
============================
448
The Bundle Buggy tool used up to May 2009 is still available as a review
451
Sending patches for review
452
--------------------------
454
If you'd like to propose a change, please post to the
455
bazaar@lists.canonical.com list with a bundle, patch, or link to a
456
branch. Put ``[PATCH]`` or ``[MERGE]`` in the subject so Bundle Buggy
457
can pick it out, and explain the change in the email message text.
458
Remember to update the NEWS file as part of your change if it makes any
459
changes visible to users or plugin developers. Please include a diff
460
against mainline if you're giving a link to a branch.
462
You can generate a merge request like this::
464
bzr send -o bug-1234.patch
466
A ``.patch`` extension is recommended instead of .bundle as many mail clients
467
will send the latter as a binary file.
469
``bzr send`` can also send mail directly if you prefer; see the help.
471
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
472
want it to be merged. If you want comments from developers rather than
473
to be merged, you can put ``[RFC]`` in the subject line.
475
If this change addresses a bug, please put the bug number in the subject
476
line too, in the form ``[#1]`` so that Bundle Buggy can recognize it.
478
If the change is intended for a particular release mark that in the
479
subject too, e.g. ``[1.6]``.
480
Anyone can "vote" on the mailing list by expressing an opinion. Core
481
developers can also vote using Bundle Buggy. Here are the voting codes and
484
:approve: Reviewer wants this submission merged.
485
:tweak: Reviewer wants this submission merged with small changes. (No
487
:abstain: Reviewer does not intend to vote on this patch.
488
:resubmit: Please make changes and resubmit for review.
489
:reject: Reviewer doesn't want this kind of change merged.
490
:comment: Not really a vote. Reviewer just wants to comment, for now.
492
If a change gets two approvals from core reviewers, and no rejections,
493
then it's OK to come in. Any of the core developers can bring it into the
494
bzr.dev trunk and backport it to maintenance branches if required. The
495
Release Manager will merge the change into the branch for a pending
496
release, if any. As a guideline, core developers usually merge their own
497
changes and volunteer to merge other contributions if they were the second
498
reviewer to agree to a change.
500
To track the progress of proposed changes, use Bundle Buggy. See
501
http://bundlebuggy.aaronbentley.com/help for a link to all the
502
outstanding merge requests together with an explanation of the columns.
503
Bundle Buggy will also mail you a link to track just your change.
505
Coding Style Guidelines
506
#######################
511
``hasattr`` should not be used because it swallows exceptions including
512
``KeyboardInterrupt``. Instead, say something like ::
514
if getattr(thing, 'name', None) is None
520
Please write PEP-8__ compliant code.
522
__ http://www.python.org/peps/pep-0008.html
524
One often-missed requirement is that the first line of docstrings
525
should be a self-contained one-sentence summary.
527
We use 4 space indents for blocks, and never use tab characters. (In vim,
530
Trailing white space should be avoided, but is allowed.
531
You should however not make lots of unrelated white space changes.
533
Unix style newlines (LF) are used.
535
Each file must have a newline at the end of it.
537
Lines should be no more than 79 characters if at all possible.
538
Lines that continue a long statement may be indented in either of
541
within the parenthesis or other character that opens the block, e.g.::
547
or indented by four spaces::
553
The first is considered clearer by some people; however it can be a bit
554
harder to maintain (e.g. when the method name changes), and it does not
555
work well if the relevant parenthesis is already far to the right. Avoid
558
self.legbone.kneebone.shinbone.toebone.shake_it(one,
564
self.legbone.kneebone.shinbone.toebone.shake_it(one,
570
self.legbone.kneebone.shinbone.toebone.shake_it(
573
For long lists, we like to add a trailing comma and put the closing
574
character on the following line. This makes it easier to add new items in
577
from bzrlib.goo import (
583
There should be spaces between function parameters, but not between the
584
keyword name and the value::
586
call(1, 3, cheese=quark)
590
;(defface my-invalid-face
591
; '((t (:background "Red" :underline t)))
592
; "Face used to highlight invalid constructs or other uglyties"
595
(defun my-python-mode-hook ()
596
;; setup preferred indentation style.
597
(setq fill-column 79)
598
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
599
; (font-lock-add-keywords 'python-mode
600
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
601
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
602
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
606
(add-hook 'python-mode-hook 'my-python-mode-hook)
608
The lines beginning with ';' are comments. They can be activated
609
if one want to have a strong notice of some tab/space usage
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.
616
28
* Imports should be done at the top-level of the file, unless there is
617
29
a strong reason to have them lazily loaded when a particular
621
33
* Module names should always be given fully-qualified,
622
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
628
Functions, methods or members that are "private" to bzrlib are given
629
a leading underscore prefix. Names without a leading underscore are
630
public not just across modules but to programmers using bzrlib as an
631
API. As a consequence, a leading underscore is appropriate for names
632
exposed across modules but that are not to be exposed to bzrlib API
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.
635
156
We prefer class names to be concatenated capital words (``TestCase``)
636
157
and variables, methods and functions to be lowercase words joined by
693
209
> factory, then yes, foo_factory is what I would use.
699
Several places in Bazaar use (or will use) a registry, which is a
700
mapping from names to objects or classes. The registry allows for
701
loading in registered code only when it's needed, and keeping
702
associated information such as a help string or description.
705
InterObject and multiple dispatch
706
=================================
708
The ``InterObject`` provides for two-way `multiple dispatch`__: matching
709
up for example a source and destination repository to find the right way
710
to transfer data between them.
712
.. __: http://en.wikipedia.org/wiki/Multiple_dispatch
714
There is a subclass ``InterObject`` classes for each type of object that is
715
dispatched this way, e.g. ``InterRepository``. Calling ``.get()`` on this
716
class will return an ``InterObject`` instance providing the best match for
717
those parameters, and this instance then has methods for operations
720
inter = InterRepository.get(source_repo, target_repo)
721
inter.fetch(revision_id)
723
``InterRepository`` also acts as a registry-like object for its
724
subclasses, and they can be added through ``.register_optimizer``. The
725
right one to run is selected by asking each class, in reverse order of
726
registration, whether it ``.is_compatible`` with the relevant objects.
731
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
732
delay importing modules until they are actually used. ``lazy_import`` uses
733
the same syntax as regular python imports. So to import a few modules in a
736
from bzrlib.lazy_import import lazy_import
737
lazy_import(globals(), """
746
revision as _mod_revision,
748
import bzrlib.transport
752
At this point, all of these exist as a ``ImportReplacer`` object, ready to
753
be imported once a member is accessed. Also, when importing a module into
754
the local namespace, which is likely to clash with variable names, it is
755
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
756
the variable is a module, and these object should be hidden anyway, since
757
they shouldn't be imported into other namespaces.
759
While it is possible for ``lazy_import()`` to import members of a module
760
when using the ``from module import member`` syntax, it is recommended to
761
only use that syntax to load sub modules ``from module import submodule``.
762
This is because variables and classes can frequently be used without
763
needing a sub-member for example::
765
lazy_import(globals(), """
766
from module import MyClass
770
return isinstance(x, MyClass)
772
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
773
object, rather than the real class.
775
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
776
Because the replacer only knows about the original name, it is unable to
777
replace other variables. The ``ImportReplacer`` class will raise an
778
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
779
happened. But it requires accessing a member more than once from the new
780
variable, so some bugs are not detected right away.
786
The null revision is the ancestor of all revisions. Its revno is 0, its
787
revision-id is ``null:``, and its tree is the empty tree. When referring
788
to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
789
code sometimes uses ``None`` for the null revision, but this practice is
793
Object string representations
794
=============================
796
Python prints objects using their ``__repr__`` method when they are
797
written to logs, exception tracebacks, or the debugger. We want
798
objects to have useful representations to help in determining what went
801
If you add a new class you should generally add a ``__repr__`` method
802
unless there is an adequate method in a parent class. There should be a
805
Representations should typically look like Python constructor syntax, but
806
they don't need to include every value in the object and they don't need
807
to be able to actually execute. They're to be read by humans, not
808
machines. Don't hardcode the classname in the format, so that we get the
809
correct value if the method is inherited by a subclass. If you're
810
printing attributes of the object, including strings, you should normally
811
use ``%r`` syntax (to call their repr in turn).
813
Try to avoid the representation becoming more than one or two lines long.
814
(But balance this against including useful information, and simplicity of
817
Because repr methods are often called when something has already gone
818
wrong, they should be written somewhat more defensively than most code.
819
The object may be half-initialized or in some other way in an illegal
820
state. The repr method shouldn't raise an exception, or it may hide the
821
(probably more useful) underlying exception.
826
return '%s(%r)' % (self.__class__.__name__,
833
A bare ``except`` statement will catch all exceptions, including ones that
834
really should terminate the program such as ``MemoryError`` and
835
``KeyboardInterrupt``. They should rarely be used unless the exception is
836
later re-raised. Even then, think about whether catching just
837
``Exception`` (which excludes system errors in Python2.5 and later) would
844
All code should be exercised by the test suite. See `Guide to Testing
845
Bazaar <../../developers/testing.html>`_ for detailed information about writing tests.
854
We have a commitment to 6 months API stability - any supported symbol in a
855
release of bzr MUST NOT be altered in any way that would result in
856
breaking existing code that uses it. That means that method names,
857
parameter ordering, parameter names, variable and attribute names etc must
858
not be changed without leaving a 'deprecated forwarder' behind. This even
859
applies to modules and classes.
861
If you wish to change the behaviour of a supported API in an incompatible
862
way, you need to change its name as well. For instance, if I add an optional keyword
863
parameter to branch.commit - that's fine. On the other hand, if I add a
864
keyword parameter to branch.commit which is a *required* transaction
865
object, I should rename the API - i.e. to 'branch.commit_transaction'.
867
When renaming such supported API's, be sure to leave a deprecated_method (or
868
_function or ...) behind which forwards to the new API. See the
869
bzrlib.symbol_versioning module for decorators that take care of the
870
details for you - such as updating the docstring, and issuing a warning
871
when the old API is used.
873
For unsupported API's, it does not hurt to follow this discipline, but it's
874
not required. Minimally though, please try to rename things so that
875
callers will at least get an AttributeError rather than weird results.
878
Deprecation decorators
879
----------------------
881
``bzrlib.symbol_versioning`` provides decorators that can be attached to
882
methods, functions, and other interfaces to indicate that they should no
883
longer be used. For example::
885
@deprecated_method(deprecated_in((0, 1, 4)))
887
return self._new_foo()
889
To deprecate a static method you must call ``deprecated_function``
890
(**not** method), after the staticmethod call::
893
@deprecated_function(deprecated_in((0, 1, 4)))
894
def create_repository(base, shared=False, format=None):
896
When you deprecate an API, you should not just delete its tests, because
897
then we might introduce bugs in them. If the API is still present at all,
898
it should still work. The basic approach is to use
899
``TestCase.applyDeprecated`` which in one step checks that the API gives
900
the expected deprecation message, and also returns the real result from
901
the method, so that tests can keep running.
903
Deprecation warnings will be suppressed for final releases, but not for
904
development versions or release candidates, or when running ``bzr
905
selftest``. This gives developers information about whether their code is
906
using deprecated functions, but avoids confusing users about things they
913
Processing Command Lines
914
------------------------
916
bzrlib has a standard framework for parsing command lines and calling
917
processing routines associated with various commands. See builtins.py
918
for numerous examples.
921
Standard Parameter Types
922
------------------------
924
There are some common requirements in the library: some parameters need to be
925
unicode safe, some need byte strings, and so on. At the moment we have
926
only codified one specific pattern: Parameters that need to be unicode
927
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
928
input into unicode in a consistent fashion, allowing trivial strings to be
929
used for programmer convenience, but not performing unpredictably in the
930
presence of different locales.
936
215
(The strategy described here is what we want to get to, but it's not
967
246
should be only in the command-line tool.
970
Progress and Activity Indications
971
---------------------------------
973
bzrlib has a way for code to display to the user that stuff is happening
974
during a long operation. There are two particular types: *activity* which
975
means that IO is happening on a Transport, and *progress* which means that
976
higher-level application work is occurring. Both are drawn together by
979
Transport objects are responsible for calling `report_transport_activity`
982
Progress uses a model/view pattern: application code acts on a
983
`ProgressTask` object, which notifies the UI when it needs to be
984
displayed. Progress tasks form a stack. To create a new progress task on
985
top of the stack, call `bzrlib.ui.ui_factory.nested_progress_bar()`, then
986
call `update()` on the returned ProgressTask. It can be updated with just
987
a text description, with a numeric count, or with a numeric count and
988
expected total count. If an expected total count is provided the view
989
can show the progress moving along towards the expected total.
991
The user should call `finish` on the `ProgressTask` when the logical
992
operation has finished, so it can be removed from the stack.
994
Progress tasks have a complex relationship with generators: it's a very
995
good place to use them, but because python2.4 does not allow ``finally``
996
blocks in generators it's hard to clean them up properly. In this case
997
it's probably better to have the code calling the generator allocate a
998
progress task for its use and then call `finalize` when it's done, which
999
will close it if it was not already closed. The generator should also
1000
finish the progress task when it exits, because it may otherwise be a long
1001
time until the finally block runs.
1007
Bazaar has online help for various topics through ``bzr help COMMAND`` or
1008
equivalently ``bzr command -h``. We also have help on command options,
1009
and on other help topics. (See ``help_topics.py``.)
1011
As for python docstrings, the first paragraph should be a single-sentence
1012
synopsis of the command.
1014
The help for options should be one or more proper sentences, starting with
1015
a capital letter and finishing with a full stop (period).
1017
All help messages and documentation should have two spaces between
1021
Handling Errors and Exceptions
1022
==============================
1024
Commands should return non-zero when they encounter circumstances that
1025
the user should really pay attention to - which includes trivial shell
1028
Recommended values are:
1031
1. Conflicts in merge-like operations, or changes are present in
1032
diff-like operations.
1033
2. Unrepresentable diff changes (i.e. binary files that we cannot show
1035
3. An error or exception has occurred.
1036
4. An internal error occurred (one that shows a traceback.)
1038
Errors are handled through Python exceptions. Exceptions should be defined
1039
inside bzrlib.errors, so that we can see the whole tree at a glance.
1041
We broadly classify errors as either being either internal or not,
1042
depending on whether ``internal_error`` is set or not. If we think it's our
1043
fault, we show a backtrace, an invitation to report the bug, and possibly
1044
other details. This is the default for errors that aren't specifically
1045
recognized as being caused by a user error. Otherwise we show a briefer
1046
message, unless -Derror was given.
1048
Many errors originate as "environmental errors" which are raised by Python
1049
or builtin libraries -- for example IOError. These are treated as being
1050
our fault, unless they're caught in a particular tight scope where we know
1051
that they indicate a user errors. For example if the repository format
1052
is not found, the user probably gave the wrong path or URL. But if one of
1053
the files inside the repository is not found, then it's our fault --
1054
either there's a bug in bzr, or something complicated has gone wrong in
1055
the environment that means one internal file was deleted.
1057
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
1058
to be added near the place where they are used.
1060
Exceptions are formatted for the user by conversion to a string
1061
(eventually calling their ``__str__`` method.) As a convenience the
1062
``._fmt`` member can be used as a template which will be mapped to the
1063
error's instance dict.
1065
New exception classes should be defined when callers might want to catch
1066
that exception specifically, or when it needs a substantially different
1069
#. If it is something that a caller can recover from, a custom exception
1072
#. If it is a data consistency issue, using a builtin like
1073
``ValueError``/``TypeError`` is reasonable.
1075
#. If it is a programmer error (using an api incorrectly)
1076
``AssertionError`` is reasonable.
1078
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
1080
Exception strings should start with a capital letter and should not have a
1081
final fullstop. If long, they may contain newlines to break the text.
1087
Do not use the Python ``assert`` statement, either in tests or elsewhere.
1088
A source test checks that it is not used. It is ok to explicitly raise
1093
* It makes the behaviour vary depending on whether bzr is run with -O
1094
or not, therefore giving a chance for bugs that occur in one case or
1095
the other, several of which have already occurred: assertions with
1096
side effects, code which can't continue unless the assertion passes,
1097
cases where we should give the user a proper message rather than an
1099
* It's not that much shorter than an explicit if/raise.
1100
* It tends to lead to fuzzy thinking about whether the check is
1101
actually needed or not, and whether it's an internal error or not
1102
* It tends to cause look-before-you-leap patterns.
1103
* It's unsafe if the check is needed to protect the integrity of the
1105
* It tends to give poor messages since the developer can get by with
1106
no explanatory text at all.
1107
* We can't rely on people always running with -O in normal use, so we
1108
can't use it for tests that are actually expensive.
1109
* Expensive checks that help developers are better turned on from the
1110
test suite or a -D flag.
1111
* If used instead of ``self.assert*()`` in tests it makes them falsely pass with -O.
1117
When you change bzrlib, please update the relevant documentation for the
1118
change you made: Changes to commands should update their help, and
1119
possibly end user tutorials; changes to the core library should be
1120
reflected in API documentation.
1125
If you make a user-visible change, please add a note to the NEWS file.
1126
The description should be written to make sense to someone who's just
1127
a user of bzr, not a developer: new functions or classes shouldn't be
1128
mentioned, but new commands, changes in behaviour or fixed nontrivial
1129
bugs should be listed. See the existing entries for an idea of what
1132
Within each release, entries in the news file should have the most
1133
user-visible changes first. So the order should be approximately:
1135
* changes to existing behaviour - the highest priority because the
1136
user's existing knowledge is incorrect
1137
* new features - should be brought to their attention
1138
* bug fixes - may be of interest if the bug was affecting them, and
1139
should include the bug number if any
1140
* major documentation changes
1141
* changes to internal interfaces
1143
People who made significant contributions to each change are listed in
1144
parenthesis. This can include reporting bugs (particularly with good
1145
details or reproduction recipes), submitting patches, etc.
251
In general tests should be placed in a file named test_FOO.py where
252
FOO is the logical thing under test. That file should be placed in the
253
tests subdirectory under the package being tested.
255
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
256
See bzrlib/selftest/test_sampler.py for a template test script.
258
Tests can be written for the UI or for individual areas of the library.
259
Choose whichever is appropriate: if adding a new command, or a new command
260
option, then you should be writing a UI test. If you are both adding UI
261
functionality and library functionality, you will want to write tests for
262
both the UI and the core behaviours. We call UI tests 'blackbox' tests
263
and they are found in bzrlib/tests/blackbox/*.py.
265
When writing blackbox tests please honour the following conventions:
267
1. Place the tests for the command 'name' in
268
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
269
to locate the test script for a faulty command.
271
2. Use the 'self.run_bzr("name")' utility function to invoke the command
272
rather than running bzr in a subprocess or invoking the
273
cmd_object.run() method directly. This is a lot faster than
274
subprocesses and generates the same logging output as running it in a
275
subprocess (which invoking the method directly does not).
277
3. Only test the one command in a single test script. Use the bzrlib
278
library when setting up tests and when evaluating the side-effects of
279
the command. We do this so that the library api has continual pressure
280
on it to be as functional as the command line in a simple manner, and
281
to isolate knock-on effects throughout the blackbox test suite when a
282
command changes it name or signature. Ideally only the tests for a
283
given command are affected when a given command is changed.
1150
The docstring of a command is used by ``bzr help`` to generate help output
1151
for the command. The list 'takes_options' attribute on a command is used by
1152
``bzr help`` to document the options for the command - the command
1153
docstring does not need to document them. Finally, the '_see_also'
1154
attribute on a command can be used to reference other related help topics.
1159
Functions, methods, classes and modules should have docstrings
1160
describing how they are used.
1162
The first line of the docstring should be a self-contained sentence.
1164
For the special case of Command classes, this acts as the user-visible
1165
documentation shown by the help command.
1167
The docstrings should be formatted as reStructuredText_ (like this
1168
document), suitable for processing using the epydoc_ tool into HTML
1171
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
1172
.. _epydoc: http://epydoc.sourceforge.net/
1181
The copyright policy for bzr was recently made clear in this email (edited
1182
for grammatical correctness)::
1184
The attached patch cleans up the copyright and license statements in
1185
the bzr source. It also adds tests to help us remember to add them
1186
with the correct text.
1188
We had the problem that lots of our files were "Copyright Canonical
1189
Development Ltd" which is not a real company, and some other variations
1190
on this theme. Also, some files were missing the GPL statements.
1192
I want to be clear about the intent of this patch, since copyright can
1193
be a little controversial.
1195
1) The big motivation for this is not to shut out the community, but
1196
just to clean up all of the invalid copyright statements.
1198
2) It has been the general policy for bzr that we want a single
1199
copyright holder for all of the core code. This is following the model
1200
set by the FSF, which makes it easier to update the code to a new
1201
license in case problems are encountered. (For example, if we want to
1202
upgrade the project universally to GPL v3 it is much simpler if there is
1203
a single copyright holder). It also makes it clearer if copyright is
1204
ever debated, there is a single holder, which makes it easier to defend
1205
in court, etc. (I think the FSF position is that if you assign them
1206
copyright, they can defend it in court rather than you needing to, and
1207
I'm sure Canonical would do the same).
1208
As such, Canonical has requested copyright assignments from all of the
1211
3) If someone wants to add code and not attribute it to Canonical, there
1212
is a specific list of files that are excluded from this check. And the
1213
test failure indicates where that is, and how to update it.
1215
4) If anyone feels that I changed a copyright statement incorrectly, just
1216
let me know, and I'll be happy to correct it. Whenever you have large
1217
mechanical changes like this, it is possible to make some mistakes.
1219
Just to reiterate, this is a community project, and it is meant to stay
1220
that way. Core bzr code is copyright Canonical for legal reasons, and
1221
the tests are just there to help us maintain that.
1224
Miscellaneous Topics
1225
####################
1230
Bazaar has a few facilities to help debug problems by going into pdb_, the
1233
.. _pdb: http://docs.python.org/lib/debugger-commands.html
1235
If the ``BZR_PDB`` environment variable is set
1236
then bzr will go into pdb post-mortem mode when an unhandled exception
1239
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
1240
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
1241
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
1242
this as Fn-Pause). You can continue execution by typing ``c``. This can
1243
be disabled if necessary by setting the environment variable
1244
``BZR_SIGQUIT_PDB=0``.
1250
Bazaar accepts some global options starting with ``-D`` such as
1251
``-Dhpss``. These set a value in `bzrlib.debug.debug_flags`, and
1252
typically cause more information to be written to the trace file. Most
1253
`mutter` calls should be guarded by a check of those flags so that we
1254
don't write out too much information if it's not needed.
1256
Debug flags may have effects other than just emitting trace messages.
1258
Run ``bzr help global-options`` to see them all.
1260
These flags may also be set as a comma-separated list in the
1261
``debug_flags`` option in e.g. ``~/.bazaar/bazaar.conf``. (Note that it
1262
must be in this global file, not in the branch or location configuration,
1263
because it's currently only loaded at startup time.) For instance you may
1264
want to always record hpss traces and to see full error tracebacks::
1266
debug_flags = hpss, error
288
We make selective use of doctests__. In general they should provide
289
*examples* within the API documentation which can incidentally be tested. We
290
don't try to test every important case using doctests -- regular Python
291
tests are generally a better solution.
293
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
295
__ http://docs.python.org/lib/module-doctest.html
300
Currently, bzr selftest is used to invoke tests.
301
You can provide a pattern argument to run a subset. For example,
302
to run just the blackbox tests, run::
304
./bzr selftest -v blackbox
306
To skip a particular test (or set of tests), you need to use a negative
308
./bzr selftest '^(?!.*blackbox)'
311
Errors and exceptions
312
=====================
314
Errors are handled through Python exceptions. They can represent user
315
errors, environmental errors or program bugs. Sometimes we can't be sure
316
at the time it's raised which case applies. See bzrlib/errors.py for
317
details on the error-handling practices.
1275
326
indexes into the branch's revision history.
1278
Unicode and Encoding Support
1279
============================
1281
This section discusses various techniques that Bazaar uses to handle
1282
characters that are outside the ASCII set.
1287
When a ``Command`` object is created, it is given a member variable
1288
accessible by ``self.outf``. This is a file-like object, which is bound to
1289
``sys.stdout``, and should be used to write information to the screen,
1290
rather than directly writing to ``sys.stdout`` or calling ``print``.
1291
This file has the ability to translate Unicode objects into the correct
1292
representation, based on the console encoding. Also, the class attribute
1293
``encoding_type`` will effect how unprintable characters will be
1294
handled. This parameter can take one of 3 values:
1297
Unprintable characters will be represented with a suitable replacement
1298
marker (typically '?'), and no exception will be raised. This is for
1299
any command which generates text for the user to review, rather than
1300
for automated processing.
1301
For example: ``bzr log`` should not fail if one of the entries has text
1302
that cannot be displayed.
1305
Attempting to print an unprintable character will cause a UnicodeError.
1306
This is for commands that are intended more as scripting support, rather
1307
than plain user review.
1308
For example: ``bzr ls`` is designed to be used with shell scripting. One
1309
use would be ``bzr ls --null --unknowns | xargs -0 rm``. If ``bzr``
1310
printed a filename with a '?', the wrong file could be deleted. (At the
1311
very least, the correct file would not be deleted). An error is used to
1312
indicate that the requested action could not be performed.
1315
Do not attempt to automatically convert Unicode strings. This is used
1316
for commands that must handle conversion themselves.
1317
For example: ``bzr diff`` needs to translate Unicode paths, but should
1318
not change the exact text of the contents of the files.
1321
``bzrlib.urlutils.unescape_for_display``
1322
----------------------------------------
1324
Because Transports work in URLs (as defined earlier), printing the raw URL
1325
to the user is usually less than optimal. Characters outside the standard
1326
set are printed as escapes, rather than the real character, and local
1327
paths would be printed as ``file://`` urls. The function
1328
``unescape_for_display`` attempts to unescape a URL, such that anything
1329
that cannot be printed in the current encoding stays an escaped URL, but
1330
valid characters are generated where possible.
1336
The ``bzrlib.osutils`` module has many useful helper functions, including
1337
some more portable variants of functions in the standard library.
1339
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
1340
to fail on Windows if some files are readonly or still open elsewhere.
1341
Use ``bzrlib.osutils.rmtree`` instead.
1347
We write some extensions in C using pyrex. We design these to work in
1350
* User with no C compiler
1351
* User with C compiler
1354
The recommended way to install bzr is to have a C compiler so that the
1355
extensions can be built, but if no C compiler is present, the pure python
1356
versions we supply will work, though more slowly.
1358
For developers we recommend that pyrex be installed, so that the C
1359
extensions can be changed if needed.
1361
For the C extensions, the extension module should always match the
1362
original python one in all respects (modulo speed). This should be
1363
maintained over time.
1365
To create an extension, add rules to setup.py for building it with pyrex,
1366
and with distutils. Now start with an empty .pyx file. At the top add
1367
"include 'yourmodule.py'". This will import the contents of foo.py into this
1368
file at build time - remember that only one module will be loaded at
1369
runtime. Now you can subclass classes, or replace functions, and only your
1370
changes need to be present in the .pyx file.
1372
Note that pyrex does not support all 2.4 programming idioms, so some
1373
syntax changes may be required. I.e.
1375
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1376
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1378
If the changes are too dramatic, consider
1379
maintaining the python code twice - once in the .pyx, and once in the .py,
1380
and no longer including the .py file.
1383
Making Installers for OS Windows
1384
================================
1385
To build a win32 installer, see the instructions on the wiki page:
1386
http://bazaar-vcs.org/BzrWin32Installer
1389
Core Developer Tasks
1390
####################
1395
What is a Core Developer?
1396
-------------------------
1398
While everyone in the Bazaar community is welcome and encouraged to
1399
propose and submit changes, a smaller team is reponsible for pulling those
1400
changes together into a cohesive whole. In addition to the general developer
1401
stuff covered above, "core" developers have responsibility for:
1404
* reviewing blueprints
1406
* managing releases (see the `Releasing Bazaar <../../developers/releasing.html>`_)
1409
Removing barriers to community participation is a key reason for adopting
1410
distributed VCS technology. While DVCS removes many technical barriers,
1411
a small number of social barriers are often necessary instead.
1412
By documenting how the above things are done, we hope to
1413
encourage more people to participate in these activities, keeping the
1414
differences between core and non-core contributors to a minimum.
1417
Communicating and Coordinating
1418
------------------------------
1420
While it has many advantages, one of the challenges of distributed
1421
development is keeping everyone else aware of what you're working on.
1422
There are numerous ways to do this:
1424
#. Assign bugs to yourself in Launchpad
1425
#. Mention it on the mailing list
1426
#. Mention it on IRC
1428
As well as the email notifcations that occur when merge requests are sent
1429
and reviewed, you can keep others informed of where you're spending your
1430
energy by emailing the **bazaar-commits** list implicitly. To do this,
1431
install and configure the Email plugin. One way to do this is add these
1432
configuration settings to your central configuration file (e.g.
1433
``~/.bazaar/bazaar.conf`` on Linux)::
1436
email = Joe Smith <joe.smith@internode.on.net>
1437
smtp_server = mail.internode.on.net:25
1439
Then add these lines for the relevant branches in ``locations.conf``::
1441
post_commit_to = bazaar-commits@lists.canonical.com
1442
post_commit_mailer = smtplib
1444
While attending a sprint, RobertCollins' Dbus plugin is useful for the
1445
same reason. See the documentation within the plugin for information on
1446
how to set it up and configure it.
1455
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1456
development itself is known as "Decentralized with automatic gatekeeper".
1457
To repeat the explanation of this given on
1458
http://bazaar-vcs.org/Workflows:
1461
In this workflow, each developer has their own branch or
1462
branches, plus read-only access to the mainline. A software gatekeeper
1463
(e.g. PQM) has commit rights to the main branch. When a developer wants
1464
their work merged, they request the gatekeeper to merge it. The gatekeeper
1465
does a merge, a compile, and runs the test suite. If the code passes, it
1466
is merged into the mainline.
1468
In a nutshell, here's the overall submission process:
1470
#. get your work ready (including review except for trivial changes)
1471
#. push to a public location
1472
#. ask PQM to merge from that location
1475
At present, PQM always takes the changes to merge from a branch
1476
at a URL that can be read by it. For Bazaar, that means a public,
1477
typically http, URL.
1479
As a result, the following things are needed to use PQM for submissions:
1481
#. A publicly available web server
1482
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1483
#. The PQM plugin installed and configured (not strictly required but
1484
highly recommended).
1487
Selecting a Public Branch Location
1488
----------------------------------
1490
If you don't have your own web server running, branches can always be
1491
pushed to Launchpad. Here's the process for doing that:
1493
Depending on your location throughout the world and the size of your
1494
repository though, it is often quicker to use an alternative public
1495
location to Launchpad, particularly if you can set up your own repo and
1496
push into that. By using an existing repo, push only needs to send the
1497
changes, instead of the complete repository every time. Note that it is
1498
easy to register branches in other locations with Launchpad so no benefits
1499
are lost by going this way.
1502
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1503
suggestion for public http branches. Contact your manager for information
1504
on accessing this system if required.
1506
It should also be noted that best practice in this area is subject to
1507
change as things evolve. For example, once the Bazaar smart server on
1508
Launchpad supports server-side branching, the performance situation will
1509
be very different to what it is now (Jun 2007).
1512
Configuring the PQM Plug-In
1513
---------------------------
1515
While not strictly required, the PQM plugin automates a few things and
1516
reduces the chance of error. Before looking at the plugin, it helps to
1517
understand a little more how PQM operates. Basically, PQM requires an
1518
email indicating what you want it to do. The email typically looks like
1521
star-merge source-branch target-branch
1525
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1527
Note that the command needs to be on one line. The subject of the email
1528
will be used for the commit message. The email also needs to be ``gpg``
1529
signed with a key that PQM accepts.
1531
The advantages of using the PQM plugin are:
1533
#. You can use the config policies to make it easy to set up public
1534
branches, so you don't have to ever type the full paths you want to merge
1537
#. It checks to make sure the public branch last revision matches the
1538
local last revision so you are submitting what you think you are.
1540
#. It uses the same public_branch and smtp sending settings as bzr-email,
1541
so if you have one set up, you have the other mostly set up.
1543
#. Thunderbird refuses to not wrap lines, and request lines are usually
1544
pretty long (you have 2 long URLs in there).
1546
Here are sample configuration settings for the PQM plugin. Here are the
1547
lines in bazaar.conf::
1550
email = Joe Smith <joe.smith@internode.on.net>
1551
smtp_server=mail.internode.on.net:25
1553
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1554
dirstate-tags branches)::
1556
[/home/joe/bzr/my-integration]
1557
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1558
push_location:policy = norecurse
1559
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1560
public_branch:policy = appendpath
1561
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1562
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1564
Note that the push settings will be added by the first ``push`` on
1565
a branch. Indeed the preferred way to generate the lines above is to use
1566
``push`` with an argument, then copy-and-paste the other lines into
1573
Here is one possible recipe once the above environment is set up:
1575
#. pull bzr.dev => my-integration
1576
#. merge patch => my-integration
1577
#. fix up any final merge conflicts (NEWS being the big killer here).
1583
The ``push`` step is not required if ``my-integration`` is a checkout of
1586
Because of defaults, you can type a single message into commit and
1587
pqm-commit will reuse that.
1590
Tracking Change Acceptance
1591
--------------------------
1593
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1594
a change, you can visit this URL to confirm it was received and placed in
1597
When PQM completes processing a change, an email is sent to you with the
1601
Reviewing Blueprints
332
The ``Transport`` layer handles access to local or remote directories.
333
Each Transport object acts like a logical connection to a particular
334
directory, and it allows various operations on files within it. You can
335
*clone* a transport to get a new Transport connected to a subdirectory or
338
Transports are not used for access to the working tree. At present
339
working trees are always local and they are accessed through the regular
340
Python file io mechanisms.
345
Transports work in URLs. Take note that URLs are by definition only
346
ASCII - the decision of how to encode a Unicode string into a URL must be
347
taken at a higher level, typically in the Store. (Note that Stores also
348
escape filenames which cannot be safely stored on all filesystems, but
349
this is a different level.)
351
The main reason for this is that it's not possible to safely roundtrip a
352
URL into Unicode and then back into the same URL. The URL standard
353
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
354
doesn't say how those bytes represent non-ASCII characters. (They're not
355
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
357
For example if the user enters the url ``http://example/%e0`` there's no
358
way to tell whether that character represents "latin small letter a with
359
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
360
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
362
Equally problematic if we're given a url-like string containing non-ascii
363
characters (such as the accented a) we can't be sure how to convert that
364
to the correct URL, because we don't know what encoding the server expects
365
for those characters. (Although this is not totally reliable we might still
366
accept these and assume they should be put into UTF-8.)
368
A similar edge case is that the url ``http://foo/sweet%2Fsour" contains
369
one directory component whose name is "sweet/sour". The escaped slash is
370
not a directory separator. If we try to convert URLs to regular Unicode
371
paths this information will be lost.
373
This implies that Transports must natively deal with URLs; for simplicity
374
they *only* deal with URLs and conversion of other strings to URLs is done
375
elsewhere. Information they return, such as from ``list_dir``, is also in
376
the form of URL components.
1602
380
====================
1604
Blueprint Tracking Using Launchpad
1605
----------------------------------
1607
New features typically require a fair amount of discussion, design and
1608
debate. For Bazaar, that information is often captured in a so-called
1609
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1610
is done using Launchpad's relevant tracker,
1611
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1612
review, please announce it on the mailing list.
1614
Alternatively, send an email beginning with [RFC] with the proposal to the
1615
list. In some cases, you may wish to attach proposed code or a proposed
1616
developer document if that best communicates the idea. Debate can then
1617
proceed using the normal merge review processes.
1620
Recording Blueprint Review Feedback
1621
-----------------------------------
1623
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1624
(Jun 2007) support a chronological list of comment responses. Review
1625
feedback can either be recorded on the Wiki hosting the blueprints or by
1626
using Launchpad's whiteboard feature.
1633
Using Releases and Milestones in Launchpad
1634
------------------------------------------
1636
TODO ... (Exact policies still under discussion)
1642
Keeping on top of bugs reported is an important part of ongoing release
1643
planning. Everyone in the community is welcome and encouraged to raise
1644
bugs, confirm bugs raised by others, and nominate a priority. Practically
1645
though, a good percentage of bug triage is often done by the core
1646
developers, partially because of their depth of product knowledge.
1648
With respect to bug triage, core developers are encouraged to play an
1649
active role with particular attention to the following tasks:
1651
* keeping the number of unconfirmed bugs low
1652
* ensuring the priorities are generally right (everything as critical - or
1653
medium - is meaningless)
1654
* looking out for regressions and turning those around sooner rather than later.
1657
As well as prioritizing bugs and nominating them against a
1658
target milestone, Launchpad lets core developers offer to mentor others in
1663
vim: ft=rst tw=74 ai
382
If you'd like to propose a change, please post to the
383
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
384
branch. Please put '[patch]' in the subject so we can pick them out, and
385
include some text explaining the change. Remember to put an update to the NEWS
386
file in your diff, if it makes any changes visible to users or plugin
387
developers. Please include a diff against mainline if you're giving a link to
390
Please indicate if you think the code is ready to merge, or if it's just a
391
draft or for discussion. If you want comments from many developers rather than
392
to be merged, you can put '[rfc]' in the subject lines.
394
Anyone is welcome to review code. There are broadly three gates for
397
* Doesn't reduce test coverage: if it adds new methods or commands,
398
there should be tests for them. There is a good test framework
399
and plenty of examples to crib from, but if you are having trouble
400
working out how to test something feel free to post a draft patch
403
* Doesn't reduce design clarity, such as by entangling objects
404
we're trying to separate. This is mostly something the more
405
experienced reviewers need to help check.
407
* Improves bugs, features, speed, or code simplicity.
409
Code that goes in should pass all three.
411
If you read a patch please reply and say so. We can use a numeric scale
412
of -1, -0, +0, +1, meaning respectively "really don't want it in current
413
form", "somewhat uncomfortable", "ok with me", and "please put it in".
414
Anyone can "vote". (It's not really voting, just a terse expression.)
416
If something gets say two +1 votes from core reviewers, and no
417
vetos, then it's OK to come in. Any of the core developers can bring it
418
into their integration branch, which I'll merge regularly. (If you do
419
so, please reply and say so.)
422
:: vim: ft=rst tw=74 ai
added
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HACKING
