~bzr-pqm/bzr/bzr.dev

==================

Bazaar-NG Tutorial

==================

current for bzr 0.0.6pre, July 2005

*NOTE* For a more current and user-editable version of this 

document, see the wiki at http://bazaar.canonical.com/IntroductionToBzr

Introduction

============

Bazaar-NG is a version control tool.  It manages trees of files and subdirectories.  In particular, it records *revisions* of trees, representing their state at a particular point in time, and information about those revisions and their relationships.  Recording and retrieving tree revisions is useful in several ways if you are writing software or documents or doing similar creative work.

 * Keeping previous revisions lets you go back if you make a mistake or want to check your work.  It acts as a high-level unlimited undo.

 * By recording comments on every revision, you produce an annotated history of the project, describing what, who, why, and when.

 * Using a version control tool can be an aid to thinking about a project: getting to a stable state at regular intervals and then writing a description of what you did is an easy way to stay organized and on track.

Bazaar-NG remembers the *ancestry* of a revision: the previous revisions that it is based upon.  A single revision may have more than one direct descendant, each with different changes, representing a divergence in the evolution of the tree.  

By branching, Bazaar-NG allows multiple people to cooperate on the evolution of a project, without all needing to work in strict

lock-step.  Branching can be useful even for a single developer.

Bazaar-NG installs a single new command,

*bzr*.  Everything else is a subcommand of this.  You can get

some help with ``bzr help``.  There will be more in the future.

Introducing yourself to bzr

===========================

One function of a version control system is to keep track of who

changed what.  In a distributed system that requires an identifier for

each author that is globally unique.  Most people already have one of

these: an email address.

[after 0.0.4] To tell bzr which email address to use, put it in the file

``$HOME/.bzr.conf/email``, or the environment variable ``$BZREMAIL``.

If neither of these are set, bzr will use the ``$EMAIL``

variable, or use your username and hostname.

To check this has taken effect, or if you forget your own name, use

the ``whoami`` ("who am i?") command::

  % bzr whoami

Some people want to avoid sharing their email address so as not to

get spam.  bzr will never

disclose your email address unless you tell it to by publishing an

archive or transmitting a changeset.  It's recommended that you do use

a real address, so that people can contact you about your work, but

it's not required.  You can use an address which is obfuscated, which

bounces, or which goes through an anti-spam service such as spamgourmet.com.

Creating a branch

==================

History is by default stored in the .bzr directory of the branch.

There will be a facility to store it in a separate repository, which

may be remote.  We create a new branch by running *bzr init* in

an existing directory::

    % mkdir tutorial

    % cd tutorial

    % ls -a

    ls -a

    ./  ../

    % pwd

    /home/mbp/work/bzr.test/tutorial

    %

    % bzr init

    % ls -aF

    ./  ../  .bzr/

    %

As for CVS, there are three classes of file: unknown, ignored, and

versioned.  The *add* command makes a file versioned: that is,

changes to it will be recorded by the system::

    % echo 'hello world' > hello.txt

    % bzr status

    ?       hello.txt

    % bzr unknowns

    hello.txt

    % bzr add -v hello.txt

    A       hello.txt

    % bzr unknowns

If you add the wrong file, simply use ``bzr remove`` to make

it unversioned again.  This does not delete the working copy.

Reviewing changes

=================

Once you have completed some work, you will want to *commit*

it to the version history.  It is good to commit fairly often:

whenever you get a new feature working, fix a bug, or improve some

code or documentation.  It's also a good practice to make sure that

the code compiles and passes its test suite before committing, to make

sure that every revision is a known-good state.  You can also review

your changes, to make sure you're committing what you intend to, and

as a chance to rethink your work before you permanently record it. 

Two bzr commands are particularly useful here: *status* and

*diff*.  The *status* command

shows a listing with one line per file, indicating whether it has been

Added, Deleted, Modified, or Renamed in the current revision.  Unknown

files are shown as '?'.  With the ``--all`` option, the status

command also shows unmodified versioned files as '.', and ignored

files as 'I'::

    % bzr status

    A       hello.txt

The *diff* command shows the full text of changes to all

files as a standard unified diff.  This can be piped through many

programs such as ``patch``, ``diffstat``,

``filterdiff`` and ``colordiff``::

    % bzr diff

    *** added file 'hello.txt'

    --- /dev/null 

    +++ hello.txt 

    @@ -1,0 +1,1 @@

    +hello world

With the ``-r`` option, the tree is compared to an earlier

revision.

[TODO: options to run external diff; to get context diff or other

formats; to diff only selected files; to compare two historical

revisions.]

Committing changes

==================

When the working tree state is satisfactory, it can be

*committed* to the branch, creating a new revision holding a

snapshot of that state.  

The ``commit`` command takes a message describing the changes

in the revision.  It also records your userid, the current time and

timezone, and the inventory and contents of the tree.  The commit

message is specified by the ``-m`` or ``--message`` option.

You can enter a multi-line commit message; in most shells you can

enter this just by leaving the quotes open at the end of the line. ::

    % bzr commit -m "added my first file"

[TODO: commit message interactively, through an editor or from a

file.]

[TODO: commit only selected files, including renamed/added/deleted

files.]

Removing uncommitted changes

============================

If you've made some changes and don't want to keep them, use the

``revert`` command to go back to the previous head version.  It's a

good idea to use ``bzr diff`` first to see what will be removed. 

By default the revert command reverts the whole tree; if file or

directory names are given then only those ones will be affected.

revert also clears the list of pending merges revisions.

Ignoring files

==============

Many source trees contain some files that do not need to be

versioned, such as editor backups, object or bytecode files, and built

programs.  You can simply not add them, but then they'll always crop

up as unknown files.  You can also tell bzr to ignore these files by

adding them to a file called ``.bzrignore`` at the top of the

tree.

This file contains a list of file wildcards (or "globs"), one

per line.  Typical contents are like this::

    *.o

    *~

    *.tmp

    *.py[co]

If a glob contains a slash, it is matched against the whole path

from the top of the tree; otherwise it is matched against only the

filename.  So the previous example ignores ``*.o`` in all

subdirectories, but this example ignores only config.h at the top

level and HTML files in ``doc/``::

    ./config.h

    doc/*.html

To get a list of which files are ignored and what pattern they matched, use ``bzr ignored``::

    % bzr ignored

    config.h                                           ./config.h

    configure.in~                                      *~

It is OK to have an ignore pattern match a versioned file, or to

add an ignored file.  Ignore patterns have no effect on versioned

files; they only determine whether unversioned files are reported as

unknown or ignored.

The ``.bzrignore`` file should normally be versioned, so that new

copies of the branch see the same patterns::

    % bzr add .bzrignore

    % bzr commit -m "Add ignore patterns"

Examining history

=================

bzr log

-------

The ``log`` command shows a list of previous revisions.

Branch statistics

=================

The ``bzr info`` command shows some summary information about

the working tree and the branch history.  

Versioning directories

======================

bzr versions files and directories in a way that can keep track of

renames and intelligently merge them::

    % mkdir src

    % echo 'int main() {}' > src/simple.c

    % bzr add src

    % bzr status

    A       src/

    ?       src/simple.c

    % bzr add src/simple.c

    % bzr status

    A       src/

    A       src/simple.c

Deleting and removing files

===========================

You can delete files or directories by just deleting them from the

working directory.  This is a bit different to CVS, which requires

that you also do *cvs remove*.

*bzr remove* makes the file un-versioned, but does not

delete the working copy.  This is useful when you add the wrong file,

or decide that a file should actually not be versioned. ::

    % rm -r src

    % bzr remove -v hello.txt

    ?       hello.txt

    % bzr status

    ?       hello.txt

    D       src/

    D       src/simple.c

Branching

=========

Often rather than starting your own project, you will want to

submit a change to an existing project.  You can get a copy of an

existing branch by copying its directory, expanding a tarball, or by a

remote copy using something like rsync.  You can also use bzr to fetch

a copy.  Because this new copy is potentially a new branch, the

command is called *branch*::

    % bzr branch http://bazaar-ng.org/bzr/bzr.dev

    % cd bzr.dev

This copies down the complete history of this branch, so we can

do all operations on it locally: log, annotate, making and merging

branches.  There will be an option to get only part of the history if

you wish.

Following upstream changes

==========================

You can stay up-to-date with the parent branch by *pulling*

in their changes::

    % bzr pull

This only works if your local branch includes only changes from the

parent branch.  Otherwise, the branches are said to have *diverged*,

and they must be merged instead.