My favorite feature of logical names was that they didn't just point to directories -- they could be a search path! To test new code, all I had to do was creat

My favorite feature of logical names was that they didn't just point to directories -- they could be a search path! To test new code, all I had to do was create a directory to hold my changes, and copy in just the files I wanted to update. Set the logical name aliasing the code location to search first in my "branch" directory, then in the main directory. Any code in found the top-level search location takes precedence over the main directory. Boom! Instant branches, but supported at the OS level.