gup updates and manages the global Go command-line tools in $GOBIN. go install places each program there but never updates it again, keeps no manifest of what it installed, and offers no way to hold a tool at a version you depend on. gup brings the whole set up to date in parallel, pins selected tools to exact versions, and adds the management commands go install lacks: list and check what is installed, remove binaries, export and import the set to reproduce it on another machine, and migrate it to a new $GOBIN.
