Implement caching for docker builder

utils.go

@@ -474,3 +474,50 @@ func FindCgroupMountpoint(cgroupType string) (string, error) {
 
 	return "", fmt.Errorf("cgroup mountpoint not found for %s", cgroupType)
 }
+
+// Compare two Config struct. Do not compare the "Image" nor "Hostname" fields
+// If OpenStdin is set, then it differs
+func CompareConfig(a, b *Config) bool {
+	if a == nil || b == nil ||
+		a.OpenStdin || b.OpenStdin {
+		return false
+	}
+	if a.AttachStdout != b.AttachStdout ||
+		a.AttachStderr != b.AttachStderr ||
+		a.User != b.User ||
+		a.Memory != b.Memory ||
+		a.MemorySwap != b.MemorySwap ||
+		a.OpenStdin != b.OpenStdin ||
+		a.Tty != b.Tty {
+		return false
+	}
+	if len(a.Cmd) != len(b.Cmd) ||
+		len(a.Dns) != len(b.Dns) ||
+		len(a.Env) != len(b.Env) ||
+		len(a.PortSpecs) != len(b.PortSpecs) {
+		return false
+	}
+
+	for i := 0; i < len(a.Cmd); i++ {
+		if a.Cmd[i] != b.Cmd[i] {
+			return false
+		}
+	}
+	for i := 0; i < len(a.Dns); i++ {
+		if a.Dns[i] != b.Dns[i] {
+			return false
+		}
+	}
+	for i := 0; i < len(a.Env); i++ {
+		if a.Env[i] != b.Env[i] {
+			return false
+		}
+	}
+	for i := 0; i < len(a.PortSpecs); i++ {
+		if a.PortSpecs[i] != b.PortSpecs[i] {
+			return false
+		}
+	}
+
+	return true
+}