Partial implementation of machine readable output.

- Implement global flag for machine readable output.
- Add machine readable output (as JSON) to list command.

cli/internal/cli.go

@@ -243,6 +243,16 @@ var DebugFlag = &cli.BoolFlag{
 	Usage:       "Show DEBUG messages",
 }
 
+// MachineReadable stores the variable from MachineReadableFlag
+var MachineReadable bool
+
+// MachineReadableFlag turns on/off machine readable output where supported
+var MachineReadableFlag = &cli.BoolFlag{
+	Name:        "machine, m",
+	Destination: &MachineReadable,
+	Usage:       "Output in a machine-readable format (where supported)",
+}
+
 // RC signifies the latest release candidate
 var RC bool