Cleanup from RJ Kroege's comments to an earlier PR

cmds/cpu/cpu.go

@@ -143,6 +143,13 @@ func newCPU(host string, args ...string) (retErr error) {
 	// Also, because of how sshd works, we need to pass in
 	// a PWD that is correct; otherwise it gets lost, since
 	// since ssh wants to simulate a login..
+	// Per rjkroege's comment:
+	// "This code for building the port and environment seems
+	//  twisty and exactly the kind of thing that would benefit
+	//  from being pulled out into utility functions that
+	//  have some tests to make sure that the environment is sane?"
+	// If you are looking for something to contribute to, here is
+	// your chance.
 	if *sshd && *srvnfs {
 		env := append(os.Environ(), "CPU_PWD="+os.Getenv("PWD"))
 		envargs := "-env=" + strings.Join(env, "\n")

cmds/cpu/doc.go

@@ -73,9 +73,6 @@
 //
 //	-9p bool
 //	      enable the 9p server in the client (default enabled)
-//	      Note that the 9p server is also enabled if the namespace
-//	      is not empty. To ensure the 9p server is not set,
-//	      cpu -9p=f -namespace=""
 //	-d
 //	      enable debug prints
 //	-dbg9p
@@ -264,10 +261,13 @@
 // Plan 9 papers on cpu, but be aware there are many subtle details visible only
 // in code.
 //
-// You can now tentatively talk to standard sshd.
+// You can now talk to a standard sshd.
 // Here is an example:
 // ./cpu -nfs=true -9p=false -d -key ~/.ssh/homemac -sp 22 127.0.0.1
-// A few things: 9p has to be off, since sshd don't understand the -9 switch
+// For this case, because it is port 22, cpu will arrange for cpuns
+// to run with the sudo command.
+// If the nfs switch is true, you must have sudo installed.
+// Also: 9p has to be off, since sshd does not understand the -9 switch.
 // Failing to Setenv is no longer an error, so you may not be able to set things
 // like SHELL.
 package main