script names are prepended to scripts that are eval'ed
but the names are missing for prescripts.

PiperOrigin-RevId: 242554372

devserver/main.go

diff --git a/devserver/main.go b/devserver/main.go
index a41b899..466a63d 100644
--- a/devserver/main.go
+++ b/devserver/main.go
@@ -130,7 +130,7 @@
 	if err != nil {
 		return "", err
 	}
-	return string(buf), nil
+	return fmt.Sprintf("// %s\n%s", path, buf), nil
 }
 
 // manifestFiles parses a manifest, returning a list of the files in the manifest.