Tooling for dealing with and understanding legacy code. Some tools are around but they're scattered. I'd like to be able to easily see what code is not in use,

Tooling for dealing with and understanding legacy code. Some tools are around but they're scattered. I'd like to be able to easily see what code is not in use, be able to generate database diagrams, see what files are changed most frequently, automatically link changes to your change bug tracking system etc. I deal with legacy code and most often the real work is in understanding why a prior change was made.