Easy logout when only one username is logged in.

Change the behaviour of the “logout” command to make the username
optional when only one user is logged in.

This does not change the behaviour of the command when a username is
given. Notably, invocation of the command with no username specified
may or may not exit with error; but the command never exits with error
when a username is specified.

command/logout.go

@@ -6,18 +6,22 @@ import (
 	"runtime"
 
 	. "github.com/heroku/force/config"
+	. "github.com/heroku/force/error"
 	. "github.com/heroku/force/lib"
 )
 
 var cmdLogout = &Command{
-	Usage: "logout",
-	Short: "Log out from force.com",
+	Usage: "logout [-u=username]",
+	Short: "Log out from Force.com",
 	Long: `
-  force logout -u=username
+Log out from Force.com
 
-  Example:
+The username may be omitted when only one account is logged in, in which case
+that single logged-in account will be logged out.
 
-    force logout -u=user@example.org
+Examples:
+  force logout
+  force logout -u=user@example.org
 `,
 }
 
@@ -26,17 +30,24 @@ func init() {
 }
 
 var (
-	userName1 = cmdLogout.Flag.String("u", "", "Username for Soap Login")
+	logoutUserName = cmdLogout.Flag.String("u", "", "Username to log out")
 )
 
 func runLogout(cmd *Command, args []string) {
-	if *userName1 == "" {
-		fmt.Println("Missing required argument...")
-		cmd.Flag.Usage()
-		return
+	/* If a username was specified, we will use it regardless of logins.
+	 * Otherwise, if there's only one login, we'll use that. */
+	if *logoutUserName == "" {
+		accounts, _ := Config.List("accounts")
+		if len(accounts) == 0 {
+			ErrorAndExit("No logins, so a username cannot be assumed.")
+		} else if len(accounts) > 1 {
+			ErrorAndExit("More than one login. Please specify a username.")
+		} else {
+			logoutUserName = &accounts[0]
+		}
 	}
-	Config.Delete("accounts", *userName1)
-	if active, _ := Config.Load("current", "account"); active == *userName1 {
+	Config.Delete("accounts", *logoutUserName)
+	if active, _ := Config.Load("current", "account"); active == *logoutUserName {
 		Config.Delete("current", "account")
 		SetActiveLoginDefault()
 	}