Enhance info endpoint to include gateway version

Extend the health endpoint and add gateway version information

Resolves: #733
Signed-off-by: Edward Wilde <ewilde@gmail.com>

gateway/tests/integration/infohandler_test.go

@@ -0,0 +1,48 @@
+package inttests
+
+import (
+	"encoding/json"
+	"net/http"
+	"testing"
+
+	"github.com/openfaas/faas/gateway/types"
+)
+
+func Test_InfoEndpoint_Returns_200(t *testing.T) {
+	_, code, err := fireRequest("http://localhost:8080/system/info", http.MethodGet, "")
+
+	if err != nil {
+		t.Log(err)
+		t.Fail()
+	}
+
+	wantCode := http.StatusOK
+	if code != wantCode {
+		t.Errorf("status code, want: %d, got: %d", wantCode, code)
+		t.Fail()
+	}
+}
+
+func Test_InfoEndpoint_Returns_Gateway_Version_SHA_And_Message(t *testing.T) {
+	body, _, err := fireRequest("http://localhost:8080/system/info", http.MethodGet, "")
+
+	if err != nil {
+		t.Log(err)
+		t.Fail()
+	}
+
+	gatewayInfo := &types.GatewayInfo{}
+	err = json.Unmarshal([]byte(body), gatewayInfo)
+	if err != nil {
+		t.Log(err)
+		t.Fail()
+	}
+
+	if len(gatewayInfo.Version.SHA) != 40 {
+		t.Errorf("length of SHA incorrect, want: %d, got: %d. Json body was %s", 40, len(gatewayInfo.Version.SHA), body)
+	}
+
+	if len(gatewayInfo.Version.CommitMessage) == 0 {
+		t.Errorf("length of commit message should be greater than 0. Json body was %s", body)
+	}
+}