fix ERL_ROOTDIR issues

see #56 (comment)

Author: jhheider

action.js

@@ -16,6 +16,11 @@ const replaceEnvVars = (str) => {
       /\$\{([a-zA-Z0-9_]+):\+:\$[a-zA-Z0-9_]+\}/g,
       (_, key) => ((v) => v ? `:${v}` : "")(process.env[key]),
     )
+    // handles ${FOO:-bar} > $FOO || "bar"
+    .replaceAll(
+      /\$\{([a-zA-Z0-9_]+):-([^}]*)\}/g,
+      (_, key, defaultVal) => process.env[key] || defaultVal,
+    )
     .replaceAll(/\$\{([a-zA-Z0-9_]+)\}/g, (_, key) => process.env[key] ?? "")
     .replaceAll(/\$([a-zA-Z0-9_]+)/g, (_, key) => process.env[key] ?? "");
   return value;