Include mu-plugins in Studio site import

[bgrgicak]

Related issues

• Fixes Consider importing mu-plugins directories #500

Proposed Changes

• Don't delete the mu-plugins/sqlite-integration-plugin folder during import
• Include mu-plugins in Playground, Jetpack, Wpress, and Local imports
• Prevent import from failing if an empty folder wasn't extracted

Testing Instructions

• Checkout this branch
• Optionally download import files with included mu-plugin folders if you don't have them already
• Start Studio

Jetpack Import

• Import the Jetpack import file
• Confirm that the site name is updated to Jetpack
• Confirm that the mu-plugins/sqlite-integration-plugin folder is present
• Confirm that a mu-plugins/jetpack.php file is present

Playground Import

• Import the Playground import file
• Confirm that the site name is updated to Playground
• Confirm that the mu-plugins/sqlite-integration-plugin folder is present
• Confirm that a mu-plugins/playground.php file is present

Wpress Import

• Import the Wpress import file
• Confirm that the site name is updated to Wpress
• Confirm that the mu-plugins/sqlite-integration-plugin folder is present
• Confirm that a mu-plugins/wpress.php file is present

Local Import

• Import the Local import file
• Confirm that the site name is updated to Local
• Confirm that the mu-plugins/sqlite-integration-plugin folder is present
• Confirm that a mu-plugins/local.php file is present

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[bgrgicak]

I discovered this issue in a Local export.
The uploads/2025/01 folder was empty on the site and the 01 folder is missing from the extracted ZIP.
This caused lstat to fail because the directory didn't exist.

[bgrgicak]

Should I make muPlugins mandatory?

[wojtekn]

Let's keep it optional, as none of the supported backup formats includes it by default.

[wojtekn]

@bgrgicak the code change looks good and works as expected for the packages you provided.

However, it doesn't work for my Playground import file, which works fine in Studio 1.3.2.

Also, we should include mu-plugins/ to export for completeness, so the site exported from Studio and imported again would have the same set of plugins. We can add a separate issue for that, though.

[wojtekn]

However, it doesn't work for my Playground import file, which works fine in Studio 1.3.2.

It seems it happens in the trunk, too. I've added https://github.com/Automattic/dotcom-forge/issues/10369

[wojtekn]

Let's keep it optional, as none of the supported backup formats includes it by default.

[wojtekn]

Also, we should include mu-plugins/ to export for completeness, so the site exported from Studio and imported again would have the same set of plugins. We can add a separate issue for that, though.

I've opened https://github.com/Automattic/dotcom-forge/issues/10373 for that.