Like many places we are slowly moving out of an era where we ran Unixes that came from the vendor with very limited amounts of packages, and so we had to build and install all sorts of them ourselves. Some of the collection we just compiled as-is, and some of it we had to modify, and some of them we wrote ourselves from scratch.

And we put the source code for all of them in the same local source tree.

Allow me to suggest that you not do this. If you keep local source code, separate it out into (at least) packages that you just (re)compiled, packages from elsewhere that you had to modify, and entirely local programs. A few years from now, this will make it much easier to figure out what you can gleefully throw out, what you might want to look through, and what you need to keep at least for reference to figure out just what it did.

Note that this applies just as much if you are building .debs or RPMs or whatever instead of just doing 'make install'. I also believe that it applies even if you are building your own entire private copy of, for example, a Ruby on Rails environment.