github/linguist — pull request #141 by semperos (2012-03-19 12:50:10+00:00)
Title: Add .lsp as an extension for Common Lisp

I've seen this used especially with newLISP, but I think giving it Common Lisp highlighting as a default makes a lot of sense.

I don't see any tests related to existing Lisp-highlighting functionality, so I haven't added any myself.