by axel.schreiner:

godoc binds GOPATH/src to /src/pkg;
i.e., directories below GOPATH/src contain packages, not commands;
i.e., HTTP requests for /cmd/FOO only work if FOO is in GOROOT/src/cmd.

Looks to me like godoc cannot readily document user-written commands outside GOROOT. (I
kludged this using -path; however, it's a very awkward, undocumented kludge.)

Note that the distributed directory structure is GOROOT/src/pkg for packages and
GOROOT/src/cmd for commands.

If godoc/main.go/main() were changed, e.g., to

    // Bind $GOPATH trees into Go root.
    for _, p := range filepath.SplitList(build.Default.GOPATH) {
        fs.Bind("/src/pkg", OS(p), "/src/pkg", bindAfter)
        fs.Bind("/src/cmd", OS(p), "/src/cmd", bindAfter)
    }

then HTTP requests /pkg/FOO and /cmd/FOO would document user packages in
GOPATH/src/pkg/FOO and commands in GOPATH/src/cmd/FOO, respectively. (This does,
however, break the current interpretation of GOPATH for godoc).

Alternatively,

    // Bind $GOPATH trees into Go root.
    for _, p := range filepath.SplitList(build.Default.GOPATH) {
        fs.Bind("/src/cmd", OS(p), "/src/cmd", bindAfter)
        fs.Bind("/src/pkg", OS(p), "/src", bindAfter)
    }

would not break the current interpretation of GOPATH and would also document user
commands. (The package list in this case shows a package 'cmd' containing directories
for user commands.)

The option -path only applies to packages because it binds each path /FOO/BAR to
/src/pkg/BAR,
i.e., an HTTP request /pkg/BAR will produce documentation from /FOO/BAR.

One could add another option -cmds to godoc/godoc.go/initHandlers() to bind paths to
/src/cmd to allow single user commands to be added to the server:

var ...
    cmdPath = flag.String("cmds", "", "additional command directories (colon-separated)")

initHandler...

    // Add named directories in -cmds argument as
    // subdirectories of src/cmd.
    for _, p := range filepath.SplitList(*cmdPath) {
        _, elem := filepath.Split(p)
        if elem == "" {
            log.Fatalf("invalid -cmds argument: %q has no final element", p)
        }
        fs.Bind("/src/cmd/"+elem, OS(p), "/", bindReplace)
    }

Which operating system are you using?
MacOS X 10.8

Which version are you using?  (run 'go version')
go1