Fix for invalid environment variable names used on windows that start with an...

Fix for invalid environment variable names used on windows that start with an equals symbol. Even though this contradicts the Microsoft docs.

caddyhttp/httpserver/context.go

@@ -64,7 +64,7 @@ func (c Context) Env() map[string]string {
 	envVars := make(map[string]string, len(osEnv))
 	for _, env := range osEnv {
 		data := strings.SplitN(env, "=", 2)
-		if len(data) == 2 {
+		if len(data) == 2 && len(data[0]) > 0 {
 			envVars[data[0]] = data[1]
 		}
 	}

caddyhttp/httpserver/context_test.go

@@ -234,6 +234,9 @@ func TestEnv(t *testing.T) {
 	notExisting := "ENV_TEST_NOT_EXISTING"
 	os.Unsetenv(notExisting)
 
+	invalidName := "ENV_TEST_INVALID_NAME"
+	os.Setenv("="+invalidName, testValue)
+
 	env := context.Env()
 	if value := env[name]; value != testValue {
 		t.Errorf("Expected env-variable %s value '%s', found '%s'",
@@ -244,6 +247,17 @@ func TestEnv(t *testing.T) {
 		t.Errorf("Expected empty env-variable %s, found '%s'",
 			notExisting, value)
 	}
+
+	for k, v := range env {
+		if strings.Contains(k, invalidName) {
+			t.Errorf("Expected invalid name not to be included in Env %s, found in key '%s'", invalidName, k)
+		}
+		if strings.Contains(v, invalidName) {
+			t.Errorf("Expected invalid name not be be included in Env %s, found in value '%s'", invalidName, v)
+		}
+	}
+
+	os.Unsetenv("=" + invalidName)
 }
 
 func TestIP(t *testing.T) {