1
.. This file is in Python ReStructuredText format - it can be formatted
2
.. into HTML or text. In the future we plan to extract the example commands
3
.. and automatically test them.
5
.. This text was previously on the wiki at
6
.. http://bazaar.canonical.com/IntroductionToBzr
7
.. but has been moved into the source tree so it can be kept in sync with
8
.. the source and possibly automatically checked.
14
Current for bzr-0.8, 2006-04
20
If you are already familiar with decentralized revision control, then
21
please feel free to skip ahead to "Introducing Yourself to Bazaar-NG". If,
22
on the other hand, you are familiar with revision control but not
23
decentralized revision control, then please start at "How DRCS is
24
different." Otherwise, get some coffee or tea, get comfortable and get
27
The Purposes of Revision Control
28
================================
30
Odds are that you have worked on some sort of textual data -- the sources
31
to a program, web sites or the config files that Unix system
32
administrators have to deal with in /etc. The chances are also good that
33
you have made some sort of mistake that you deeply regretted. Perhaps you
34
deleted the configuration file for your mailserver or perhaps mauled the
35
source code for a pet project. Whatever happened, you have just deleted
36
important information that you would desperately like to get back. If this
37
has ever happened to you, then you are probably ready for Bazaar-NG.
39
Revision control systems (which I'll henceforth call RCS) such as
40
Bazaar-NG give you the ability to track changes for a directory by turning
41
it into something slightly more complicated than a directory that we call
42
a **branch**. The branch not only stores how the directory looks right
43
now, but also how it looked at various points in the past. Then, when you
44
do something you wish you hadn't, you can restore the directory to the way
45
it looked at some point in the past.
47
Revision control systems give users the ability to save changes to a
48
branch by "committing a **revision**". The revision created is essentially
49
a summary of the changes that were made since the last time the tree was
52
These revisions have other uses as well. For example, one can comment
53
revisions to record what the recent set of changes meant by providing an
54
optional log message. Real life log messages include things like "Fixed
55
the web template to close the table" and "Added sftp suppport. Fixes #595"
57
We keep these logs so that if later there is some sort of problem with
58
sftp, we can figure out when the problem probably happened.
63
Many Revision Control Systems (RCS) are stored on servers. If one wants to
64
work on the code stored within an RCS, then one needs to connect to the
65
server and "checkout" the code. Doing so gives one a directory in which a
66
person can make changes and then commit. The RCS client then connects to
67
the RCS server and stores the changes. This method is known as the
70
The centralized model can have some drawbacks. A centralized RCS requires
71
that one is able to connect to the server whenever one wants to do version
72
control work. This can be a bit of a problem if your server on some other
73
machine on the internet and you are not. Or, worse yet, you ''are'' on the
74
internet but the server is missing!
76
Decentralized Revision Control Systems (which I'll call DRCS after this
77
point) deal with this problem by keeping branches on the same machine as
78
the client. In Bazaar-NG's case, the branch is kept in the same place as
79
the code that is being version controlled. This allows the user to save
80
his changes (**commit**) whenever he wants -- even if he is offline. The
81
user only needs internet access when he wants to access the changes in
82
someone else's branch that are somewhere else.
85
A common requirement that many people have is the need to keep track of
86
the changes for a directory such as file and subdirectory changes.
87
Performing this tracking by hand is a awkward process that over time
88
becomes unwieldy. That is, until one considers version control tools such
89
as Bazaar-NG. These tools automate the process of storing data by creating
90
a **revision** of the directory tree whenever the user asks.
92
Revision control software such as Bazaar-NG can do much more than just
93
storage and performing undo. For example, with Bazaar-NG developer can
94
take the modifications in one branch of software and apply them to
95
another, related, branch -- even if those changes exist in a branch owned
96
by somebody else. This allows developers to cooperate without giving write
99
Bazaar-NG remembers the ''ancestry'' of a revision: the previous revisions
100
that it is based upon. A single revision may have more than one direct
101
descendant, each with different changes, representing a divergence in the
102
evolution of the tree. By branching, Bazaar-NG allows multiple people to
103
cooperate on the evolution of a project, without all needing to work in
104
strict lock-step. Branching can be useful even for a single developer.
106
Introducing yourself to Bazaar-NG
107
=================================
109
Bazaar-NG installs a single new command, **bzr**. Everything else is a
110
subcommand of this. You can get some help with `bzr help`. There will be
113
One function of a version control system is to keep track of who changed
114
what. In a decentralized system, that requires an identifier for each
115
author that is globally unique. Most people already have one of these: an
116
email address. Bzr is smart enough to automatically generate an email
117
address by looking up your username and hostname. If you don't like the
118
guess that Bazaar-NG makes, then three options exist:
120
1. Setting the email address in the
121
``~/.bazaar/bazaar.conf`` by adding the following lines. Please note that
122
``[DEFAULT]`` is case sensitive::
125
email= Your Name <email@isp.com>
127
1. Override the previous setting on a
128
branch by branch basis by creating a branch section in
129
``~/.bazaar/branches.conf`` by adding the following lines::
131
[/the/directory/to/the/branch]
132
email=Your Name <email@isp.com>
134
1. Overriding the two previous options by setting the global environment
135
variable ``$BZREMAIL`` or ``$EMAIL`` (``$BZREMAIL`` will take precedence)
136
to your full email address.
141
History is by default stored in the .bzr directory of the branch. There
142
will be a facility to store it in a separate repository, which may be
143
remote. We create a new branch by running **bzr init** in an existing
151
/home/mbp/work/bzr.test/tutorial
158
As for CVS, there are three classes of file: unknown, ignored, and
159
versioned. The **add** command makes a file versioned: that is, changes
160
to it will be recorded by the system::
162
% echo 'hello world' > hello.txt
173
If you add the wrong file, simply use **bzr remove** to make it
174
unversioned again. This does not delete the working copy.
179
All history is stored in a branch, which is just an on-disk directory
180
containing control files. By default there is no separate repository or
181
database as used in svn or svk. You can choose to create a repository if
182
you want to (see the **bzr init-repo** command). You may wish to do this
183
if you have very large branches, or many branches of a moderate sized
186
You'll usually refer to branches on your computer's filesystem just by
187
giving the name of the directory containing the branch. bzr also supports
188
accessing branches over http, for example::
190
% bzr log http://bazaar-ng.org/bzr/bzr.dev/
192
By installing bzr plugins you can also access branches over the sftp or
198
Once you have completed some work, you will want to **commit** it to the
199
version history. It is good to commit fairly often: whenever you get a
200
new feature working, fix a bug, or improve some code or documentation.
201
It's also a good practice to make sure that the code compiles and passes
202
its test suite before committing, to make sure that every revision is a
203
known-good state. You can also review your changes, to make sure you're
204
committing what you intend to, and as a chance to rethink your work before
205
you permanently record it.
207
Two bzr commands are particularly useful here: **status** and **diff**.
212
The **status** command tells you what changes have been made to the
213
working directory since the last revision::
219
By default **bzr status** hides "boring" files that are either unchanged
220
or ignored. To see them too, use the --all option. The status command
221
can optionally be given the name of some files or directories to check.
226
The **diff** command shows the full text of changes to all files as a
227
standard unified diff. This can be piped through many programs such as
228
''patch'', ''diffstat'', ''filterdiff'' and ''colordiff''::
231
*** added file 'hello.txt'
238
With the ''-r'' option, the tree is compared to an earlier revision, or
239
the differences between two versions are shown::
241
% bzr diff -r 1000.. # everything since r1000
242
% bzr diff -r 1000..1100 # changes from 1000 to 1100
244
The --diff-options option causes bzr to run the external diff program,
245
passing options. For example::
247
% bzr diff --diff-options --side-by-side foo
249
Some projects prefer patches to show a prefix at the start of the path for
250
old and new files. The --prefix option can be used to provide such a prefix.
251
As a shortcut, ``bzr diff -p1`` produces a form that works with the
252
command ``patch -p1``.
257
When the working tree state is satisfactory, it can be **committed** to
258
the branch, creating a new revision holding a snapshot of that state.
263
The **commit** command takes a message describing the changes in the
264
revision. It also records your userid, the current time and timezone, and
265
the inventory and contents of the tree. The commit message is specified
266
by the ''-m'' or ''--message'' option. You can enter a multi-line commit
267
message; in most shells you can enter this just by leaving the quotes open
268
at the end of the line.
272
% bzr commit -m "added my first file"
274
You can also use the -F option to take the message from a file. Some
275
people like to make notes for a commit message while they work, then
276
review the diff to make sure they did what they said they did. (This file
277
can also be useful when you pick up your work after a break.)
279
Message from an editor
280
======================
282
If you use neither the `-m` nor the `-F` option then bzr will open an
283
editor for you to enter a message. The editor to run is controlled by
284
your `$EDITOR` environment variable or
285
add `editor` to ~/.bazaar/bazaar.conf; `$BZR_EDITOR` will override
286
the above mentioned editor options. If you quit the editor without
287
making any changes, the commit will be cancelled.
292
If you give file or directory names on the commit command line then only
293
the changes to those files will be committed. For example::
295
% bzr commit -m "documentation fix" commit.py
297
By default bzr always commits all changes to the tree, even if run from a
298
subdirectory. To commit from only the current directory down, use::
303
Removing uncommitted changes
304
============================
306
If you've made some changes and don't want to keep them, use the
307
**revert** command to go back to the previous head version. It's a good
308
idea to use **bzr diff** first to see what will be removed. By default the
309
revert command reverts the whole tree; if file or directory names are
310
given then only those ones will be affected. **revert** also clears the
311
list of pending merges revisions.
316
Many source trees contain some files that do not need to be versioned,
317
such as editor backups, object or bytecode files, and built programs. You
318
can simply not add them, but then they'll always crop up as unknown files.
319
You can also tell bzr to ignore these files by adding them to a file
320
called ''.bzrignore'' at the top of the tree.
322
This file contains a list of file wildcards (or "globs"), one per line.
323
Typical contents are like this::
330
If a glob contains a slash, it is matched against the whole path from the
331
top of the tree; otherwise it is matched against only the filename. So
332
the previous example ignores files with extension ``.o`` in all
333
subdirectories, but this example ignores only config.h at the top level
334
and HTML files in ``doc/``::
339
To get a list of which files are ignored and what pattern they matched,
340
use ''bzr ignored''::
346
It is OK to have either an ignore pattern match a versioned file, or to
347
add an ignored file. Ignore patterns have no effect on versioned files;
348
they only determine whether unversioned files are reported as unknown or
351
The ''.bzrignore'' file should normally be versioned, so that new copies
352
of the branch see the same patterns::
355
% bzr commit -m "Add ignore patterns"
364
The **bzr log** command shows a list of previous revisions. The **bzr log
365
--forward** command does the same in chronological order to get most
366
recent revisions printed at last.
368
As with bzr diff, bzr log supports the -r argument::
370
% bzr log -r 1000.. # Revision 1000 and everything after it
371
% bzr log -r ..1000 # Everything up to and including r1000
372
% bzr log -r 1000..1100 # changes from 1000 to 1100
373
% bzr log -r 1000 # The changes in only revision 1000
379
The **bzr info** command shows some summary information about the working
380
tree and the branch history.
383
Versioning directories
384
======================
386
bzr versions files and directories in a way that can keep track of renames
387
and intelligently merge them::
390
% echo 'int main() {}' > src/simple.c
395
% bzr add src/simple.c
401
Deleting and removing files
402
===========================
404
You can delete files or directories by just deleting them from the working
405
directory. This is a bit different to CVS, which requires that you also
408
**bzr remove** makes the file un-versioned, but does not delete
409
the working copy. This is useful when you add the wrong file, or decide
410
that a file should actually not be versioned.
415
% bzr remove -v hello.txt
422
If you remove the wrong file by accident, you can use **bzr revert** to
429
Often rather than starting your own project, you will want to submit a
430
change to an existing project. You can get a copy of an existing branch
431
by copying its directory, expanding a tarball, or by a remote copy using
432
something like rsync. You can also use bzr to fetch a copy. Because this
433
new copy is potentially a new branch, the command is called *branch*::
435
% bzr branch http://bazaar-ng.org/bzr/bzr.dev
438
This copies down the complete history of this branch, so we can do all
439
operations on it locally: log, annotate, making and merging branches.
440
There will be an option to get only part of the history if you wish.
442
Following upstream changes
443
==========================
445
You can stay up-to-date with the parent branch by "pulling" in their
450
After this change, the local directory will be a mirror of the source. This
451
includes the ''revision-history'' - which is a list of the commits done in
452
this branch, rather than merged from other branches.
454
This command only works if your local (destination) branch is either an
455
older copy of the parent branch with no new commits of its own, or if the
456
most recent commit in your local branch has been merged into the parent
459
Merging from related branches
460
=============================
462
If two branches have diverged (both have unique changes) then **bzr
463
merge** is the appropriate command to use. Merge will automatically
464
calculate the changes that exist in the branch you're merging from that
465
are not in your branch and attempt to apply them in your branch.
472
If there is a conflict during a merge, 3 files with the same basename are
473
created. The filename of the common base is appended with .BASE, the
474
filename of the file containing your changes is appended .THIS and the
475
filename with the changes from the other tree is appended .OTHER.
476
Using a program such as kdiff3, you can now comfortably merge them into
477
one file. To commit you have to rename it to the original basename and
478
delete the other two files. As long as there exist files with .BASE, .THIS
479
or .OTHER the commit command will complain.
481
[**TODO**: explain conflict markers within files]
484
Publishing your branch
485
======================
487
You don't need a special server to publish a bzr branch, just a normal web
488
server. Just mirror the files to your server, including the .bzr
489
directory. One can push a branch (or the changes for a branch) by one of
490
the following three methods:
492
* Rsync: rsync -avrz LOCALBRANCH servername.com/this/directory/here
494
(or any other tool for publishing a directory to a web site.)
496
* bzr push sftp://servername.com/this/directory/here
498
(The directory that must already exist)
500
* The push plugin that comes with BzrTools
added
removed
doc/tutorial.txt
