put Linux build files inside a folder before zipping (#870)

* add preference to set a custom update url

* put linux build inside a folder before zipping

electron/packager/utils.js

@@ -50,6 +50,67 @@ function collectUnusedDependencies(pathToProject = process.cwd()) {
   });
 }
 
+/**
+ * `pathToZip` is a `path/to/your/app-name.zip`.
+ * If the `pathToZip` archive does not have a root directory with name `app-name`, it creates one, and move the content from the
+ * archive's root to the new root folder. If the archive already has the desired root folder, calling this function is a NOOP.
+ * If `pathToZip` is not a ZIP, rejects. `targetFolderName` is the destination folder not the new archive location.
+ */
+function adjustArchiveStructure(pathToZip, targetFolderName, noCleanup) {
+  return new Promise(async (resolve, reject) => {
+    if (!(await isZip(pathToZip))) {
+      reject(new Error(`Expected a ZIP file.`));
+      return;
+    }
+    if (!fs.existsSync(targetFolderName)) {
+      reject(new Error(`${targetFolderName} does not exist.`));
+      return;
+    }
+    if (!fs.lstatSync(targetFolderName).isDirectory()) {
+      reject(new Error(`${targetFolderName} is not a directory.`));
+      return;
+    }
+    console.log(`⏱️  >>> Adjusting ZIP structure ${pathToZip}...`);
+
+    const root = basename(pathToZip);
+    const resources = await list(pathToZip);
+    const hasBaseFolder = resources.find((name) => name === root);
+    if (hasBaseFolder) {
+      if (
+        resources.filter((name) => name.indexOf(path.sep) === -1).length > 1
+      ) {
+        console.warn(
+          `${pathToZip} ZIP has the desired root folder ${root}, however the ZIP contains other entries too: ${JSON.stringify(
+            resources
+          )}`
+        );
+      }
+      console.log(`👌  <<< The ZIP already has the desired ${root} folder.`);
+      resolve(pathToZip);
+      return;
+    }
+
+    const track = temp.track();
+    try {
+      const unzipOut = path.join(track.mkdirSync(), root);
+      fs.mkdirSync(unzipOut);
+      await unpack(pathToZip, unzipOut);
+      const adjustedZip = path.join(targetFolderName, path.basename(pathToZip));
+      await pack(unzipOut, adjustedZip);
+      console.log(
+        `👌  <<< Adjusted the ZIP structure. Moved the modified ${basename(
+          pathToZip
+        )} to the ${targetFolderName} folder.`
+      );
+      resolve(adjustedZip);
+    } finally {
+      if (!noCleanup) {
+        track.cleanupSync();
+      }
+    }
+  });
+}
+
 /**
  * Returns the `basename` of `pathToFile` without the file extension.
  */
@@ -152,6 +213,7 @@ function getChannelFile(platform) {
 
 module.exports = {
   collectUnusedDependencies,
+  adjustArchiveStructure,
   isZip,
   unpack,
   isNightly,