Support for placeholders in fastcgi env vars.

caddyhttp/httpserver/replacer.go

@@ -127,6 +127,11 @@ func NewReplacer(r *http.Request, rr *ResponseRecorder, emptyValue string) Repla
 // Replace performs a replacement of values on s and returns
 // the string with the replaced values.
 func (r *replacer) Replace(s string) string {
+	// Do not attempt replacements if no placeholder is found.
+	if !strings.ContainsAny(s, "{}") {
+		return s
+	}
+
 	// Make response placeholders now
 	if r.responseRecorder != nil {
 		r.replacements["{status}"] = strconv.Itoa(r.responseRecorder.status)

caddyhttp/httpserver/replacer_test.go

@@ -32,7 +32,7 @@ func TestNewReplacer(t *testing.T) {
 		if got, want := v.replacements["{status}"], ""; got != want {
 			t.Errorf("Expected status to NOT be set before Replace() is called; was: %s", got)
 		}
-		rep.Replace("foobar")
+		rep.Replace("{foobar}")
 		if got, want := v.replacements["{status}"], "200"; got != want {
 			t.Errorf("Expected status to be %s, was: %s", want, got)
 		}