Improve getFileType

- Change parameter name
- Add more documentation

lib/actions-util.js

@@ -382,12 +382,16 @@ function getWorkflowRunAttempt() {
 exports.getWorkflowRunAttempt = getWorkflowRunAttempt;
 /**
  * Tries to obtain the output of the `file` command for the file at the specified path.
+ * The output will vary depending on the type of `file`, which operating system we are running on, etc.
  */
-const getFileType = async (fp) => {
+const getFileType = async (filePath) => {
     let stderr = "";
     let stdout = "";
     try {
-        await new toolrunner.ToolRunner(await safeWhich.safeWhich("file"), ["-L", fp], {
+        // The `file` command will output information about the type of file pointed at by `filePath`.
+        // For binary files, this may include e.g. whether they are static of dynamic binaries.
+        // The `-L` switch instructs the command to follow symbolic links.
+        await new toolrunner.ToolRunner(await safeWhich.safeWhich("file"), ["-L", filePath], {
             silent: true,
             listeners: {
                 stdout: (data) => {
@@ -401,7 +405,7 @@ const getFileType = async (fp) => {
         return stdout;
     }
     catch (e) {
-        core.info(`Could not determine type of ${fp} from ${stdout}. ${stderr}`);
+        core.info(`Could not determine type of ${filePath} from ${stdout}. ${stderr}`);
         throw e;
     }
 };