Using version control (SVN, CVS, etc) keywords for program logic

Question

On a couple of projects now, I've used the SVN keywords to retrieve some information about the version of some core files. Something like this (PHP):

$revision = '$Revision: 1254 $'; // automatically updated each commit
$revision = preg_replace("/[^0-9]/", "");

echo "This file is at revision #" . $revision;

It occurred to me however, by inspecting the $URL$ keyword output, I could tell if the current file was in a tag, branch or on the trunk and apply different logic to the program, eg, increase the cache times, etc.

$svnURL = '$URL: path/to/repo/tags/1.0.1/folder/file.txt $';
if (strpos($svnURL, "/tags/") !== false) {
    echo "Tagged version!";
}

Is this veering sharply into WTF territory, or would you consider this practice to be acceptable?

Answer 1

Mm, that's veering into WTF world as far as I'm concerned.

Better off configuring those things as environment variables in a general place in your application.

Answer 2

In my opinion, using the SVN keywords to affect program logic is a little bit obscure. I don't feel it qualifies as pathological, but it would surely require some explanatory comments.

Also, in your example, you simply echo what amounts to version information. I take it from what you wrote that you intend actually to decrease the cache time for your tagged version. As that aids debugging and is specific to your internal practices, I can see why you might want to do this.

Answer 3

This is a really bad idea, IMO. If you need configuration management, do it using configuration files and conditionals. Don't depend on your source code control system for configuration management.

Answer 4

Not a good idea. A much better way to achieve this would be to assign the version/build number as part of of a continuous integration or build process. This can be done in .Net by changing the AssemblyInfo.cs file before building.

Answer 5

I would consider this unacceptable, because you may at some point in the future migrate to a different source control system, whereupon this house of cards would come crashing down. It would come crashing down in a way that was (a) hard to detect, and (b) hard to fix.