Version Control: Importance, Tools, and Systems, Slides of Computer Science

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Version Control

Why version control?

• Scenario 1:
  • Your program is working
  • You change “just one thing”
  • Your program breaks
  • You change it back
  • Your program is still broken-- why?
• Has this ever happened to you?

Version control for teams

• Scenario:
  • You change one part of a program--it works
  • Your co-worker changes another part--it works
  • You put them together--it doesn’t work
  • Some change in one part must have broken something in the other part
  • What were all the changes?

Teams (part 2)

• Scenario:
  • You make a number of improvements to a class
  • Your co-worker makes a number of different improvements to the same class
• How can you merge these changes?

jDiff

• jDiff is a plugin for the jEdit editor
• Advantages:
  • Everything is color coded
  • Uses synchronized scrolling
  • It's inside an editor--you can make changes directly
• Disadvantages:
  • Not stand-alone, but must be used within jDiff
  • Just a diff tool, not a complete solution

jDiff

sccs

• sccs is Source Code Control System (UNIX)
• sccs keeps multiple versions of a complete directory
• Storage requirements are small, because sccs:
  • keeps the original documents
  • keeps the changes needed to go from one version to the next
  • generates any version when you ask for it

rcs

• rcs is Revision Control System (also UNIX)
• rcs is like sccs, and does the same things, but
  • sccs keeps the originals, and applies changes to get to newer versions
  • rcs keeps the current versions, and applies changes to get back to older versions
• (Opinion) You usually want to work with the newer versions, so rcs is usually the better choice

Who cares about UNIX?

• CVS (Concurrent Versions System) is the most popular version control system on Windows
• CVS is built on top of rcs
• CVS is built into JBuilder and Eclipse
• “There are two ways to run CVS on Windows 95/NT. The first is as a client, talking to a CVS server on a Unix box. This is the recommended setup and is commonly used.” -- http://www.cvshome.org/dev/codewindow.html

CVS commands

• cvs checkout file
• cvs commit file
• cvs diff file
• These are CVS commands under UNIXPopular GUIs on Windows: - tkCVS - jCVS - WinCVS