WIP: added fallback env

task/env/env.go

@@ -95,3 +95,33 @@ func ExpandEnv(env []string, input []string) []string {
 	}
 	return input
 }
+
+func FallbackEnv(env []string, fallbacks []string) []string {
+	envMap := make(map[string]string)
+	for _, e := range env {
+		key, value, ok := strings.Cut(e, "=")
+		if !ok {
+			wingmate.Log().Warn().Msgf("removing bad environment:", e)
+			continue
+		}
+		envMap[key] = value
+	}
+
+	for _, e := range fallbacks {
+		key, value, ok := strings.Cut(e, "=")
+		if !ok {
+			wingmate.Log().Warn().Msgf("removing bad environment:", e)
+			continue
+		}
+
+		value = envCapture.ReplaceAllStringFunc(value, func(rep string) string {
+			return expandEnv(envMap, rep)
+		})
+
+		if _, ok = envMap[key]; !ok {
+			env = append(env, fmt.Sprintf("%s=%s", key, value))
+		}
+	}
+
+	return env
+}