we're looking for a way to reliably obtain a definite, working version of the CE source code. As it is now, the source behind this page:
seems to change at will yet without signifying having done so; the only information the end user (us) can see is the name of the link, which never changes, even as the backing files do change.
This results in different versions being downloaded at different times and no one knows which version they actually have. The versions are incompatible and many times they don't work in various ways, such as the main build.xml failing, which means there is no artifact directory for that build.
The other alternative is to clone the git repository. This can change hourly and many of the changes will prevent the source from even making- they break the build. and even if they don't, getting the same version of the source code is more or less impossible.
What we are wanting is this. A certain, definite, uniquely named version of the source code where everything works for each major version of intellij. So right now that would mean a single unchanging 13.0.0 CE source code base is made available. Then when 14 comes out, the same thing. This would act as a reference version so that everyone could be on the same page, looking and working with the same thing.
Of course there would be bugs that would never realize fixes, but if the code is released from the source of major releases, it would be, by definition, a useable and mostly correct source code base with which to work and the amorphous, mutating source code base problem would be solved.
Periodically it would be great to have bug fixes integrated into this definite release so long as that release had another name. The important thing is that useable static version of the source code needs to exist somewhere publicly to act as a shared reference point.
The source code for all released versions should be available at http://download.jetbrains.com/idea/ideaIC-x.y.z-src.tar.bz2. As for code releases between major builds with a "uniquely named version", that sounds like the EAP (Early Access Builds) to me. Those builds are periodically released and have build numbers. Take a Look at the EAP page. I do not believe those releases are archived however. So you will need to grab them when they are current.
I think the problem is that you checkout a git branch and not a tag. All releases are tagged and their source code is easily available: https://github.com/JetBrains/intellij-community/releases