Do not hide .git in zip for Windows (#39432)

dev/bots/prepare_package.dart

@@ -414,9 +414,14 @@ class ArchiveCreator {
   }
 
   /// Create a zip archive from the directory source.
-  Future<String> _createZipArchive(File output, Directory source) {
+  Future<String> _createZipArchive(File output, Directory source) async {
     List<String> commandLine;
     if (platform.isWindows) {
+      // Unhide the .git folder, https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/attrib.
+      await _processRunner.runProcess(
+        <String>['attrib', '-h', '.git'],
+        workingDirectory: Directory(source.absolute.path),
+      );
       commandLine = <String>[
         '7za',
         'a',

dev/bots/test/prepare_package_test.dart

@@ -122,6 +122,7 @@ void main() {
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
           'git clean -f -X **/.packages': null,
+          if (platform.isWindows) 'attrib -h .git': null,
           if (platform.isWindows) '7za a -tzip -mx=9 $archiveName flutter': null
           else if (platform.isMacOS) 'zip -r -9 $archiveName flutter': null
           else if (platform.isLinux) 'tar cJf $archiveName flutter': null,
@@ -156,6 +157,7 @@ void main() {
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
           'git clean -f -X **/.packages': null,
+          if (platform.isWindows) 'attrib -h .git': null,
           if (platform.isWindows) '7za a -tzip -mx=9 $archiveName flutter': null
           else if (platform.isMacOS) 'zip -r -9 $archiveName flutter': null
           else if (platform.isLinux) 'tar cJf $archiveName flutter': null,
@@ -205,6 +207,7 @@ void main() {
           '$flutter create --template=package ${createBase}package': null,
           '$flutter create --template=plugin ${createBase}plugin': null,
           'git clean -f -X **/.packages': null,
+          if (platform.isWindows) 'attrib -h .git': null,
           if (platform.isWindows) '7za a -tzip -mx=9 $archiveName flutter': null
           else if (platform.isMacOS) 'zip -r -9 $archiveName flutter': null
           else if (platform.isLinux) 'tar cJf $archiveName flutter': null,