Version Control Software: Subversion

Dr. Lawlor, CS 202, CS, UAF

So in a big project, emailing software back and forth gets to be really unworkable: nobody knows what's the latest version, everybody's constantly emailing each other copies and partial updates, and there is no single working version.

There is a better way to share code, called version control.

The basic idea is to store the current version of the code on a server somewhere, and everbody can "check out" (co) a new clean copy, "update" their copy to have the latest changes, "check in" (ci) their changes, and "blame" changes on a particular version.

Here's a narrative example of how this usually goes:

Developer BILL	Developer TED
OK, first I need to set up my copy of the project. BILL$ svn co http://www.cs.uaf.edu/2010/svn/202demo Checked out revision 0.
Hmm, looks like there aren't any files yet. I'll make a file "test.cpp", and check it in. Oops, I have to "add" it first, then check it in! BILL/202demo$ notepad test.cpp BILL/202demo$ svn ci test.cpp svn: Commit failed (details follow): svn: 'BILL/202demo/test.cpp' is not under version control BILL/202demo$ svn add test.cpp A test.cpp BILL/202demo$ svn ci test.cpp Adding test.cpp Transmitting file data . Committed revision 1.
	I wonder what's happening with the project? Better set up my copy: TED/$ svn co http://www.cs.uaf.edu/2010/svn/202demo/ A 202demo/test.cpp Checked out revision 1.
	Good--looks like Bill actually wrote a "test.cpp". But it doesn't compile. I'll fix it, then check in my copy: TED/202demo$ svn ci test.cpp Sending test.cpp Transmitting file data . Committed revision 2.
Nice! Ted fixed my code. I'll grab the updated version. BILL/202demo$ svn update U test.cpp Updated to revision 2.
Now I'll do some more work on the file, and check mine in. BILL/202demo$ svn ci test.cpp Sending test.cpp Transmitting file data . Committed revision 3.	I have some more work to do on that file. I'll modify my copy, and check it in: TED/202demo$ svn ci Sending test.cpp svn: Commit failed (details follow): svn: File or directory 'test.cpp' is out of date; try updating svn: resource out of date; try updating svn: Your commit message was left in a temporary file
	Oops! I guess I need to update first, to get BILL's changes: TED/202demo$ svn update G test.cpp Updated to revision 3.
	Looks like subversion managed to integrate Bill's changes with mine. I wonder what those changes were? TED/202demo$ svn annotate test.cpp 1 - #include <iostream> 1 - 1 - int main() { 3 - std::cout<<"Woa!\n"; 2 - std::cout<<"Sup!\n"; 1 - return 0; 1 - }
	OK, that will work. Now I'll check in my modified copy: TED/202demo$ svn ci Sending test.cpp Transmitting file data . Committed revision 4.
OK, back to work. Let's see if there are any changes. BILL/202demo$ svn update U test.cpp Updated to revision 4.
Let me change that first line: BILL/202demo$ svn ci Sending test.cpp Transmitting file data . Committed revision 5.	Let me change that first line.
	Now I'll do an update before checking in. TED/202demo$ svn update Conflict discovered in 'test.cpp'. Select: (p) postpone, (df) diff-full, (e) edit, (h) help for more options: df --- .svn/text-base/test.cpp.svn-base Wed Apr 28 17:31:13 2010 +++ .svn/tmp/tempfile.3.tmp Wed Apr 28 17:31:52 2010 @@ -1,7 +1,11 @@ #include <iostream> int main() { - std::cout<<"Woa!\n"; +<<<<<<< .mine + std::cout<<"WWWWWWWoa!\n"; +======= + std::cout<<"DUUUDE. Woa!\n"; +>>>>>>> .r5 std::cout<<"Sup!\n"; std::cout<<"Man!\n"; return 0; Select: (p) postpone, (df) diff-full, (e) edit, (r) resolved, (h) help for more options: p C test.cpp Updated to revision 5.
	Oops! Bill changed the same line I did, so Subversion didn't know how to fix that. I'll manually fix this conflict, and then check in normally.

Subversion commands:

"svn co": check out a new copy of the code.
"svn update": bring your copy to the latest version (reading and merging changes from other folks).
"svn ci": check in or commit your changes (writing them to the server)
"svn add": add a file to version control.
"svn diff": compare your file with your last updated version. Useful if you forgot what you changed!
"svn log": print out the history of a file.
More options are listed in the Subversion book.

Versions of Subversion:

For Windows, TortiseSVN is pretty good, with explorer integration. Just right-click, hit TortiseSVN, and "Checkout..." a new archive.
For Mac OS, XCode comes with SVN integration. Just hit the "SCM" menu, and add your repository. The "svn" command-line application above works in a terminal, too!
Linux machines have "svn" as a built-in command (or install with "sudo apt-get install svn")
Note that it's way easier to use a repository than set one up, which requires a server, typically running Apache.

I created a Subversion repository on the www.cs server for each of your projects--feel free to use this, or try out in the 202demo repository!