SVN Subversion A brief overview

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SVN (Subversion)A brief overview?
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Why people use a version control system?

• The main benefit of using a version control
  system is that it is to allows people to share
  open source projects with ensuring changes made
  by one developer are not accidentally removed or
  altered when another developer posts their
  changes to the projects

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What is SVN?

• SVN or Subversion is a Software Engineering tool
  which is used by many software developers to
  maintain changes within their source code tree.
• SVN is popular in the open source community and
  used by many open source project, such as Apache
  Software Foundation, KDE, GNOME, Python, and
  etc.
• SVN runs on all modern flavours of UNIX, Win32,
  BeOS, OS/2, and MacOS X

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SVNs History

• In early 2000, CollabNet Inc. tried to write a
  replacement for CVS because of its limitation.
• Bad News for them! CVS had become the de facto
  standard in the open source world! Why? Because
  people had no choice but CVS!
• CollabNet determined to write a new version
  control system from scratch! BUT based on CVS and
  using CVS
• Their objectives- Maintain version control
  methodology- Match CVSs features and preserve
  the same development model- Make it similar, so
  that any CVS user could switch to it with little
  effort
• Finally, in August 2001 Subversion became free
  from CVS!!!

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Features of SVN

• Directory versioning- SVN implements a virtual
  file system which tracks changes to whole
  directory trees over time
• True version history- can add, delete, copy, and
  rename BOTH files and directories.
• Atomic commits- prevent problems that can occur
  when only a portion of a set of changes is
  successfully sent to the repository. Revision
  numbers are per-commit, not per-file log
  messages are attached to the revision, not stored
  redundantly as in CVS.
• Versioned metadata- metadata of files and
  directories can also be versioned.
• Choice of network layers- Multiple repository
  access protocols HTTP and HTTPS (Apache network
  server option, with WebDAV/DeltaV protocol)?

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Features of SVN (Continued)?

• Consistent data handling- Using a binary
  differencing algorithm, works on both text and
  binary files. File differences are transmitted in
  both directions across the network (client
  repository server)?
• Efficient branching and tagging- create branches
  and tags by copying projects (like hard-link),
  take a small amount of time
• Hackability- implemented as a collection of
  shared C libraries. Extremely maintainable and
  usable by other applications and languages.

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SVN vs. CVS

• CVS
• Pros- widely used, well documented- supported
  everywhere
• Cons- allows to commit only files- slower-
  intended to store text data, require
  specialinformation for other types of files

• SVN
• Pros- versioned renames, moves of BOTH files and
  directories- overall revision number easier
  vesioning and regression testing- prevent
  accidental committing of conflicted files-
  support for custom diff command
• Cons- need twice much space than CVS- no
  rollback of commit need to store good repository
  state to overwrite bad commit- not widely used,
  more implementation is need

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Subversions architecture

• On one end is a Subversion repository that holds
  all of your versioned data. On the other end is
  your Subversion client program, which manages
  local reflections of portions of that versioned
  data (called working copies). Between these
  extremes are multiple routes through various
  Repository Access (RA) layers. Some of these
  routes go across computer networks and through
  network servers which then access the repository.
  Others bypass the network altogether and access
  the repository directly.

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SVNs current problems

• SVN does not have built-in tools which allow
  permanent edits to the repository simply. Get
  around dump the repository, editing the result
  text file, and then recreate the repository.
• Rename operation Use copy and delete, but still
  use the same name in the older revisions.
  Confusion would occur if one uses the old name to
  create a new file and commit it to the
  repository.
• Subversion does not currently implement any
  obliterate functionality to completely remove a
  file from the repository and reclaim disk space
• Subversion stores additional copies of data on
  the local machine, which can be an issue for very
  large projects or files, or if developers are
  working on multiple branches simultaneously

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More Info?

• There is a simple explanation of SVN on Wikipedia
  ?
• SVN official webpage http//subversion.tigris.or
  g/
• SVN documentation http//svnbook.red-bean.com/
• CVS to SVN Crossover Guide http//svn.collab.net
  /repos/svn/trunk/doc/user/cvs-crossover-guide.html
  
• Subversion in GNOME http//developer.gnome.org/t
  ools/svn.html
• SVN Tutorial sites http//artis.imag.fr/Xavier.
  Decoret/resources/svn/index.htmlhttp//www.german
  e-software.com/ser/Files/Software/svntutorial.htm
  l