1. Source Control
Landscape
Lorna Jane Mitchell
PHP London, October 2010

2. About Me
 Lorna Jane Mitchell
 Freelance PHP consultant/developer/trainer
 Speaker and Writer
 Based in Leeds, UK (in town for FOWA)
 Homepage: http://lornajane.net
 Twitter: @lornajane

3. Source Control
 Tool
 History
 Subversion
 The future: DVCS

4. Subversion (svn)
Creator CollabNet
URL http://subversion.apache.org
Maintainer Apache
Users PHP
Sourceforge
FreeBSD
Apache Software
Foundation
License Apache/BSD style
Documentation Excellent, more mature
Red Bean Book
4

5. Subversion: The Roapmap
 Taken from:
● http://lwn.net/Articles/381794/
Subversion exists to be universally recognized and
adopted as an open-source, centralized version control
system characterized by its reliability as a safe haven
for valuable data; the simplicity of its model
and usage; and its ability to support the needs of a wide
variety of users and projects, from individuals to
large-scale enterprise operations.
5

6. Git
Creator Linus Torvalds
URL http://git-scm.com/
Maintainer Junio Hamano
Users Linux kernel
Ruby on Rails
CakePHP
Debian
GNOME
License GPL
Documentation "terse", a lot of
documentation for an
unfamiliar system
6

7. Bazaar (bzr)
Creator Martin Pool
URL http://bazaar.canonical.com/
Maintainer Canonical
Users Ubuntu
MySQL
Inkscape
Squid
License GPL
Documentation Excellent! Aimed at
beginners, UI designed to
be intuitive
7

8. Mercurial (hg)
Creator Matt Mackall
URL http://mercurial.selenic.com/
Maintainer Matt Mackall
Users Mozilla
OpenOffice.org
SymbianOS
NetBeans
License GPL
Documentation Good, online book and
command line help
8

9. Features
 Atomic commits
 File renames
 Symbolic links
 Pre/Post event hooks
 Merge tracking
 Tags
 EOL conversions
9

10. Protocols
 Everything supports SSH and HTTP(S)
 Distributed systems support email
 Bazaar supports FTP
 Git supports rsync
10

11. Centralised vs Distributed Source
Control
11

12. Centralised Source Control
 Traditional model
 Subversion uses this
 Other products can do it
12

13. Centralised Source Control
13

14. Distributed Source Control
14

15. Distributed Source Control
 Same function as centralised source control
 Very different approach
 Steeper learning curve
 Key concepts
● local repositories
● revisions
● branching
15

16. Local Repository
 Clone a whole repo
 It's FAST
 Can commit without sharing
 Can rewrite history
16

17. Snapshots vs Changesets
 From a Joel Spolsky post:
With distributed version control, the
distributed part is actually not the most
interesting part.
The interesting part is that these systems
think in terms of changes, not in terms of
versions
17

18. Snapshots vs Changesets
 Subversion commit is a snapshot of the
codebase
 For a DCVS, it's a set of changes
 Makes it easier to share changes
 Can be applied in different orders
 Cherry-picking

19. Branching
 Branches in DCVS are not just copies
 Working copy can switch between them
 Private branching

20. The Social Aspect

21. Hosted Code Solutions
 Combat the complexity of DCVS
 Supporting tools
 e.g. GitHub

22. Code Hosting and Collaboration
 Provide repository space
 Repo browsing, linked projects
 Forums and mailing lists
 Wiki (or similar: launchpad has blueprints)
 Publish downloadable versions
 Message other collaborators
22

23. Code Hosting Providers
GitHub git
http://github.com/
Bitbucket hg
http://bitbucket.org/
Google Code svn, hg
http://code.google.com/
Launchpad bzr
https://launchpad.net/
SourceForge svn, bzr, hg, git (and cvs)
http://sourceforge.net/
23

24. Tools and Choices

25. Trac
 Trac supports all mentioned products
 Code browsing
 Commit messages update issues

26. GUI Tools
 Moving target!
 Improving IDE support
 Tortoise* products
 Limited support for git on windows

27. Building Bridges
 Bridge between SVN repo and local
● bzr-svn https://launchpad.net/bzr-svn
● git-svn http://www.kernel.org/pub/software/scm/git/docs/git-svn.html
 Local distributed-style repo
 Communicates with central SVN server
 Pulls complete history
● diff, log fast and offline
 Work offline, commit later
27

28. Access Control
 SVN has granular access control
 Can use various apache mechanisms
 Control access by path
 DCVS are much newer, access control uses
hooks
 Can control writes
 What about reads?

29. Cost of Transition
 Steeper learning curve
 Implementation costs
● tool migration
● process changes
● supporting tool migration
● user training (ongoing!)
 Hype and dismissive attitudes are unhelpful
29

30. Making Choices
 Global team of expert geeks - use DCVS (any
one)
 Colocated team of mixed ability - use SVN
 Everything else is a sliding scale!
 Consider
● Your people
● Your admins
● The documentation, support and community of your
chosen solution
30

31. Any Questions?
31

32. Thanks!
@lornajane
http://lornajane.net