Subversion

1
Subversion

• Or, how I learned to stop worrying and love
  making changes
• http//svnbook.red-bean.com/

2
The basics

• What it is
• Why youd want to use it
• Key features

3
The Basics What it is

• A version control system for text and binary
  files, designed as a replacement for CVS
• Uses client-server model
• A filesystem based repository that stores the
  revisions of all files and metadata in your
  project is the server
• The program svn that manages your working copy is
  the client
• Allows multiple clients to work on the same
  datastore without overwriting data

4
File sharing issues
Overwriting
Lock dependecy
5
The fix Copy-Modify-Merge
Working copies
Merge Changes
6
The Basics why use it?

• Teams centralize files and documents
  eliminate data overwriting
• Individuals simple granular backups
  complete file history is always
  available
• To err is human, to forgive is divine. If youre
  not using some sort of automated version control
  on your projects, get started. It WILL be helpful.

7
The Basics Key Features

• Stores directory based version history
• Changes to a repository (commits) are atomic no
  partial commits
• Good network support
• Stand-alone svnserve (can be tunneled through
  ssh)
• Plugin for Apache 2
• Cheap, fast copying and repository reorganization
  
• Compared to other packages http//better-scm.ber
  lios.de/comparison/comparison.html

8
Getting started

• Initial Configuration
• Setting up a repository
• Importing your source files
• Checking out a working copy
• Basic Workflow
• Updating your working copy
• Committing changes
• Resolving conflicts

9
Getting Started Initial Configuration

• Setting up a repository
• Choice of filesystem (FSFS) or database
  (Berekeley DB) for persistence use FSFS unless
  you know you shouldnt
• svnadmin create /path/to/repos
• Importing files
• Recommended repository structure (trunk, branches
  and tags)
• Existing files svn import /path/to/files
  protocol//path/to/repos
• No files yet? No biggie.
• Checking out a working copy
• The working copy is the set of files you modify,
  independent of any other user
• svn checkout protocol//path/to/repos
  /path/to/wc

10
Getting started Basic Workflow

• Updating your working copy
• Merge changes made to any files in the repository
  with your working copy
• svn update
• Committing changes
• Make some changes to your codebase
• svn commit m your log message
• Resolving conflicts
• Another developer was working on the same lines
  of code and committed changes between your last
  update and now your working copy is conflicted
  with the repository
• 3 new temp files are created file.mine,
  file.rBASE, file.rHEAD
• Either merge the files by hand, use one of the
  three temp files or revert your changes (replace
  your edited file with file.rBASE)
• svn resolved filename

11
Getting started Branches

• A good way to explore different approaches to a
  problem
• Branches are copies of a set of files in the
  repository the new copies retain a revision
  history
• svn copy protocol//path/to/repos/trunk/weirdProj
  protocol//path/to/repos/branch/weirdProj
• Now you can checkout a working copy of the
  branch, and commit freely without breaking code
  for other users in the trunk
• Use svn merge protocol//path/to/repos/dir1protoc
  ol//path/to/repos/dir2my-working-copyto move
  code changes from a branch to a working copy of
  the trunk or vice versa

12
Hosting your repository

• Locally
• Working copy and repository are located on the
  same machine
• Accessible via file// protocol
• Good choice for lone developers
• No need for network access
• Repositories can be moved, if your needs change
• Can work for teams with a development server too
• Remotely
• Working copy and repository are located on
  different machines
• Accessible via svnserve (svn//, svnssh//)
• Accessible via Apache 2.0 using mod_dav and
  mod_dav_svn (http//, https//)
• Hosted
• Let someone else do it for you!
• Many options, some free, detailed here
  http//www.snook.ca/archives/servers/hosted_subver
  sion/

13
Extending subversion

• Use subversion to manage deploying to the web
• Add custom functionality with hook scripts
• Tools to simplify your experience

14
Extending deploy for the web

• You have a production site that needs to be
  updated every now and then. Sound familiar?
• Make the site a working copy!
• When updates need to be pushed to production, run
  svn update
• Stop worrying about missing dependencies
• Never edit this working copy, and you wont have
  any conflicts
• Simple to roll back to earlier file versions with
  svn revert (though this does not scale well, if
  youre reverting individual files)

15
Extending hooks

• Provides a number of hooks (think of them as
  events) which can execute arbitrary code when
  triggered
• Hook scripts can be written in any scripting
  language the server supports, including PHP
  (using the CLI executable)
• Scripts live in /path/to/repo/hooks and are
  eponymous (i.e. an executable file named
  post-commit)
• svnlook can be executed via PHP to get data about
  the repository
• exec(/usr/bin/svnlook author /path/to/repos r
  100) returns steve
• Examples
• Send an email after a successful commit
  (post-commit hook)
• Run svn update on a working copy after a
  successful commit (post-commit hook)
• Ensure log messages are properly formatted before
  a commit (pre-commit hook)
• Rebuild your phpdocs after a successful commit
  (post-commit hook)

16
Extending tools

• Web
• WebSVN (http//websvn.tigris.org/) - PHP
• SVNWeb (http//freshmeat.net/projects/svnweb/)
  - Perl
• Trac (http//trac.edgewall.org/) - Python
• Hook Scripts
• Crank HTML/RSS from log messages
  (http//www.svn2rss.com/)
• Commits as Basecamp Messages (http//simongate.com
  /2007/6/5/basecamp-post-commit-hook)
• GUI
• RapidSVN (http//rapidsvn.tigris.org/)
• TortoiseSVN (Windows http//tortoisesvn.net/)
• Kdesvn (Linux http//www.alwins-world.de/programs
  /kdesvn/)