Introduction to Bazaar
adaptive version control

Who am I?
 Tim Penhey
 http://how­bazaar.blogspot.com
 https://launchpad.net/~thumper
 Currently employed by Canonical
 http://canonical.com
 Work on Launchpad integrating Bazaar
 https://launchpad.net/launchpad­bazaar

Version Control is Good
”Those who cannot learn from history
are doomed to repeat it”
­­ George Santayana

Because this sucks
$ cp myfile.txt myfile.txt.20090120
$ ls myfile*
myfile.txt.bak
myfile.txt
myfile.txt.20090120
myfile.txt.20081218

Older Version Control Systems
 SCCS
 RCS
 CVS
 Subversion
 SourceSafe (the less said about this the better)
 Perforce

Distributed is Better
 Sometimes you cannot reach the central server
 e.g. A laptop on the move
 Should still be able to record changes in a
meaningful manner
 A local history is available

Which trunk is true?
 If everyone has a local copy of the project,
who's copy is the ”true trunk”?
 Projects that use distributed version control use
social convention

Bazaar Concepts
 Branches
 Revisions
 Repositories
 Working Trees
 Formats

What is a branch?
 A line of development
 Common to use feature branches
 this is where each feature is developed in its own
branch
 Lives in a directory on the filesystem
 all branches are addressable with a URI
 web or filesystem addressable

What is a revision?
 A revision is a collection of modifications
 e.g. an applied patch
 e.g. updated foo.c and foo.h
 Has a committer
 The person who called `bzr commit`
 May have a different author
 Allows work to be attributed to someone else
 Has a unique identifier (revision id)

What is a branch?
 A pointer to a tip revision
 a revision has one parent for a simple commit
 a revision has multiple parents for merges
 A directed acyclic graph of revisions
 and you though graph theory had no practical
applications

What is a repository?
 a set of revisions

What is a working tree?
 The actual source files that you look at and
interact with

What is a format?
 Each 'object' in Bazaar has a disk format
 Formats allow for a smooth upgrade path
 Developers knew that they weren't perfect and
planned for future improvements
 `bzr upgrade` used to move to newer shiney
formats

Simple Example
$ cd my­project
$ bzr init
$ bzr add
added hello.txt
$ bzr commit
Committed revision 1.

Sharing your work
 The push command pushes your work to a
different location
 bzr push ~/public_html/my­project
 Bazaar remembers this location so next time all
you need to do is:
 bzr push

Collaborating
 Get someone else's work
 bzr branch http://example.com/fooix/feature­x
 Merge it in with your work
 bzr merge ../feature­x
 (you don't actually need to get it first, you can just
merge in the remote branch)
 Commit – bzr doesn't auto commit
 Enjoy distributed goodness

Launchpad

Launchpad
 Bazaar hosting
 Code reviews
 Managing projects and teams
 Bug tracking
 Translations
 Personal Package Archives (PPAs)

Sharing with Launchpad
 Register
 Add an SSH key
 Push up a branch related to a project:
 bzr push lp:~user­name/project­name/branch­name
 Push up a branch of unrelated stuff:
 bzr push lp:~user­name/+junk/branch­name

Projects in Launchpad
 Projects can specify a main branch
 bzr branch lp:project­name
 Projects can have multiple series
 bzr branch lp:bzr/1.10
 bzr branch lp:bzr/1.11

Bazaar Goodness

bzr shelve
 Works on uncommitted work by default
 Can refer to historical changes
 Puts changes on a shelf
 (a directory out of the way)
 Can either put all changes '­a' flag, or
interactively choose changes
 unshelve brings the changes back

Plug­ins
 Extensibility through plug­ins
 Can add new commands or modify existing
ones
 bzr­svn – Interact with Subversion
 bzr­email – Send emails of changes
 bzrtools – Extra useful commands
 Can even add new formats
 bzr­loom – Work with a stack of lightweight
branches

Loggerhead

Familiarity
 Commands that relate clearly to other VCSs
 blame (annotate)
 commit
 log
 update
 status

Sensible ignored files
 By default
 *.a, *.o, *.py[co], *.so, *.sw[nop], *~, .#*, [#]*#
 More can be added easily
 bzr ignore *.dll
 Project specific ignores are stored in .bzrignore
 Just because something is ignored, doesn't
mean it can't be added

Aliases
$ bzr alias
bzr alias commit=”commit ­­strict”
bzr alias ll=”log ­­line ­r ­10..­1
bzr alias unalias=”alias ­­remove”

Well tested
 Development follows test driven development
practices – and has done from the start
 All new code needs test coverage
 Over 10,000 tests
 All tests are run on every attempted merge into
trunk

Other misc bits
 Clear API
 Useful when writing plug­ins
 Tool integration through XML interface
 It just works
 Doesn't get in the way

Bazaar's Curse
 Too adaptive?
 Local repository or remote repository
 Bound or unbound branches
 Lightweight / heavyweight checkouts
 Repositories with or without working trees