diff --git a/main.js b/main.js
index 3cb8b900..99cf8472 100644
--- a/main.js
+++ b/main.js
@@ -1,3 +1,14 @@
+// This is a script that just calls the bash script that does the main
+// processing of the action. It works like a composite action that calls
+// a single bash script.
+//
+// This was originally a trick adopted to make bash script-based actions work
+// without docker before composite actions were supported. However, due to
+// various problems with composite actions, this trick is still needed:
+// - https://github.com/actions/runner/issues/665
+// - https://github.com/actions/runner/issues/1947
+// - https://github.com/actions/runner/issues/2185
+
 const { execFileSync } = require('child_process');
 
 function main() {