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Version Control

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?. Why version control? (part 2). Your program worked well enough yesterday

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Version Control

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  1. Version Control

  2. 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?

  3. Why version control? (part 2) • Your program worked well enough yesterday • You made a lot of improvements last night... • ...but you haven't gotten them to work yet • You need to turn in your program now • Has this ever happened to you?

  4. 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?

  5. 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?

  6. diff tools • There are a number of tools that help you spot changes (differences) between two files • Tools include diff, rcsdiff, jDiff, etc. • Of course, they won't help unless you kept a copy of the older version • Differencing tools are useful for finding a small number of differences in a few files

  7. 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

  8. jDiff

  9. Version control systems • A version control system (often called a source code control system) does these things: • Keeps multiple (older and newer) versions of everything (not just source code) • Requests comments regarding every change • Allows “check in” and “check out” of files so you know which files someone else is working on • Displays differences between versions

  10. 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

  11. 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

  12. rcs commands • Create a directory for your rcs files • co -l file-- check out a file and lock it • Locking means you can check the file back in • ci file -- check in a revision (put file under rcs control) • rcs -l file-- lock a file you already checked out • (Needed when you checked it out and forgot the-l) • rcsdiff files-- report differences between files • merge files -- merges two files into original file • Not magic--you have to check the results

  13. 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

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

  15. CVS home page • http://www.cvshome.org

  16. The End

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