perf(copy): parallel copy

lib/copy/copy.js

@@ -113,6 +113,8 @@ async function onDir (srcStat, destStat, src, dest, opts) {
     await fs.mkdir(dest)
   }
 
+  const promises = []
+
   // loop through the files in the current directory to copy everything
   for await (const item of await fs.opendir(src)) {
     const srcItem = path.join(src, item.name)
@@ -122,13 +124,17 @@ async function onDir (srcStat, destStat, src, dest, opts) {
     const include = await runFilter(srcItem, destItem, opts)
     if (!include) continue
 
-    const { destStat } = await stat.checkPaths(srcItem, destItem, 'copy', opts)
-
-    // If the item is a copyable file, `getStatsAndPerformCopy` will copy it
-    // If the item is a directory, `getStatsAndPerformCopy` will call `onDir` recursively
-    await getStatsAndPerformCopy(destStat, srcItem, destItem, opts)
+    promises.push(
+      stat.checkPaths(srcItem, destItem, 'copy', opts).then(({ destStat }) => {
+        // If the item is a copyable file, `getStatsAndPerformCopy` will copy it
+        // If the item is a directory, `getStatsAndPerformCopy` will call `onDir` recursively
+        return getStatsAndPerformCopy(destStat, srcItem, destItem, opts)
+      })
+    )
   }
 
+  await Promise.all(promises)
+
   if (!destStat) {
     await fs.chmod(dest, srcStat.mode)
   }