fs: enable configmap to be able to tell values set vs config file values #4996

This adds AddOverrideGetter and GetOverride methods to config map and
uses them in fs.ConfigMap.

This enables us to tell which values have been set and which are just
read from the config file or at their defaults.

This also deletes the unused AddGetters method in configmap.

fs/config/configmap/configmap_test.go

@@ -90,6 +90,56 @@ func TestConfigMapSet(t *testing.T) {
 	}, m2)
 }
 
+func TestConfigMapGetOverride(t *testing.T) {
+	m := New()
+
+	value, found := m.GetOverride("config1")
+	assert.Equal(t, "", value)
+	assert.Equal(t, false, found)
+
+	value, found = m.GetOverride("config2")
+	assert.Equal(t, "", value)
+	assert.Equal(t, false, found)
+
+	m1 := Simple{
+		"config1": "one",
+	}
+
+	m.AddOverrideGetter(m1)
+
+	value, found = m.GetOverride("config1")
+	assert.Equal(t, "one", value)
+	assert.Equal(t, true, found)
+
+	value, found = m.GetOverride("config2")
+	assert.Equal(t, "", value)
+	assert.Equal(t, false, found)
+
+	m2 := Simple{
+		"config1": "one2",
+		"config2": "two2",
+	}
+
+	m.AddGetter(m2)
+
+	value, found = m.GetOverride("config1")
+	assert.Equal(t, "one", value)
+	assert.Equal(t, true, found)
+
+	value, found = m.GetOverride("config2")
+	assert.Equal(t, "", value)
+	assert.Equal(t, false, found)
+
+	value, found = m.Get("config1")
+	assert.Equal(t, "one", value)
+	assert.Equal(t, true, found)
+
+	value, found = m.Get("config2")
+	assert.Equal(t, "two2", value)
+	assert.Equal(t, true, found)
+
+}
+
 func TestSimpleString(t *testing.T) {
 	// Basic
 	assert.Equal(t, "", Simple(nil).String())