main: instantiate the config and set it up

config.go

@@ -67,6 +67,21 @@ func LoadConfig(path string) (*Config, error) {
 	return &result, nil
 }
 
+// Merge merges two configurations and returns a third entirely
+// new configuration with the two merged.
+func (c1 *Config) Merge(c2 *Config) *Config {
+	var result Config
+	result.Providers = make(map[string]string)
+	for k, v := range c1.Providers {
+		result.Providers[k] = v
+	}
+	for k, v := range c2.Providers {
+		result.Providers[k] = v
+	}
+
+	return &result
+}
+
 // ProviderFactories returns the mapping of prefixes to
 // ResourceProviderFactory that can be used to instantiate a
 // binary-based plugin.

config_test.go

@@ -26,3 +26,32 @@ func TestLoadConfig(t *testing.T) {
 		t.Fatalf("bad: %#v", c)
 	}
 }
+
+func TestConfig_Merge(t *testing.T) {
+	c1 := &Config{
+		Providers: map[string]string{
+			"foo": "bar",
+			"bar": "blah",
+		},
+	}
+
+	c2 := &Config{
+		Providers: map[string]string{
+			"bar": "baz",
+			"baz": "what",
+		},
+	}
+
+	expected := &Config{
+		Providers: map[string]string{
+			"foo": "bar",
+			"bar": "baz",
+			"baz": "what",
+		},
+	}
+
+	actual := c1.Merge(c2)
+	if !reflect.DeepEqual(actual, expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}

main.go

@@ -91,6 +91,15 @@ func wrappedMain() int {
 		log.SetOutput(logOutput)
 	}
 
+	// Load the configuration
+	config := BuiltinConfig
+
+	// Make sure we clean up any managed plugins at the end of this
+	defer plugin.CleanupClients()
+
+	// Initialize the TFConfig settings for the commands...
+	TFConfig.Providers = config.ProviderFactories()
+
 	// Get the command line args. We shortcut "--version" and "-v" to
 	// just show the version.
 	args := os.Args[1:]
@@ -110,9 +119,6 @@ func wrappedMain() int {
 		HelpFunc: cli.BasicHelpFunc("terraform"),
 	}
 
-	// Make sure we clean up any managed plugins at the end of this
-	defer plugin.CleanupClients()
-
 	exitCode, err := cli.Run()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error executing CLI: %s\n", err.Error())