Update Docker debugging.

app/lib/docker.js

@@ -5,7 +5,7 @@ import fs from 'fs'
 export default class Dockerfile extends Regex {
   constructor (root = null) {
     root = path.join(process.env.GITHUB_WORKSPACE, root)
-
+    core.debug(fs.readdirSync(root))
     if (fs.statSync(root).isDirectory()) {
       root = path.join(root, 'Dockerfile')
     }