Add filter argument to getNewestFile

Add filter predicate to allow filtering out files that are not desired
from getNewestFile.  This is useful for filtering out .tmp.zip files.

lib/fileOps/fileOps.js

@@ -5,17 +5,20 @@ const path = require("path");
  * Returns the newest file in a directory
  *
  * @param {string} directory - The directory to look for the newest file in.
- * @returns {string|null}
+ * @param {function(string): boolean} filter -
+ *     Optional function to filter out files to ignore.  Should return true
+ *     if the file is to be considered.
+ * @returns {?string}
  *     Name of the file with the newest timestamp or null if the
  *     directory contains no files.
  */
-async function getNewestFile(directory) {
+async function getNewestFile(directory, filter = (name) => true) {
 	let newestTime = new Date(0);
 	let newestFile = null;
 	for (let entry of await fs.readdir(directory, { withFileTypes: true })) {
 		if (entry.isFile()) {
 			let stat = await fs.stat(path.join(directory, entry.name));
-			if (stat.mtime > newestTime) {
+			if (filter(entry.name) && stat.mtime > newestTime) {
 				newestTime = stat.mtime;
 				newestFile = entry.name;
 			}

test/lib/fileOps/fileOps.js

@@ -21,6 +21,10 @@ describe("fileOps.js", function(){
 			let newest = await fileOps.getNewestFile(path.join(baseDir, "test"));
 			assert.equal(typeof newest, "string");
 		});
+		it("returns null if all entries were filtered out", async function() {
+			let newest = await fileOps.getNewestFile(path.join(baseDir, "test"), (name) => !name.endsWith(".txt"));
+			assert.equal(newest, null);
+		});
 		it("returns null if directory is empty", async function() {
 			let newest = await fileOps.getNewestFile(path.join(baseDir, "test", "folder"));
 			assert.equal(newest, null);