Follow linked folders (#36)

* Update archiver dependency

* Support compressing symlinks on Windows

- Add test cases for file and directory symlinks
- Add support for compressing file and symlinks on Windows
- Test on Windows 10 node 12.16.1
- Test on Ubuntu 18.04 node 12.16.1 both with and without native zip
available in path.

* Fix EMFILE error, too many open readStream issue.

.gitignore

@@ -1,6 +1,8 @@
 node_modules/
 .idea
 tmp/
+test/fixtures/subdir-symlink
+test/fixtures/file-symlink.txt
 test/validArchive.zip
 test/validARchiveExtract
 .DS_Store

lib/bestzip.js

@@ -82,6 +82,18 @@ const nodeZip = options =>
       }
     }
 
+    function walkDir(fullPath) {
+      const files = fs.readdirSync(fullPath).map(f => {
+        const filePath = path.join(fullPath, f);
+        const stats = fs.statSync(filePath);
+        if (stats.isDirectory()) {
+          return walkDir(filePath);
+        }
+        return filePath;
+      });
+      return files.reduce((acc, cur) => acc.concat(cur), []);
+    }
+
     function addSource(source, next) {
       const fullPath = path.resolve(cwd, source);
       const destPath = source;
@@ -90,7 +102,14 @@ const nodeZip = options =>
           return next(err);
         }
         if (stats.isDirectory()) {
-          archive.directory(fullPath, destPath);
+          // Walk directory. Works on directories and directory symlinks.
+          const files = walkDir(fullPath);
+          files.forEach(f => {
+            const subPath = f.substring(fullPath.length);
+            archive.file(f, {
+              name: destPath + subPath
+            });
+          });
         } else if (stats.isFile()) {
           archive.file(fullPath, { stats: stats, name: destPath });
         }