Add occ preview:migrate to migrate previews from the old flat structure to a subfolder structure

* `php occ preview:repair` - a preview migration tool that moves existing previews into the new location introduced with #19214
* moves `appdata_INSTANCEID/previews/FILEID` to `appdata_INSTANCEID/previews/0/5/8/4/c/e/5/FILEID`
* migration tool can be stopped during migration via `CTRL+C` - it then finishes the current folder (with the previews of one file) and stops gracefully
* if a PHP memory limit is set in the `php.ini` then it will stop automatically once it has less than 25 MiB memory left (this is to avoid hard crashes in the middle of a migration)
* the tool can be used during operation - possible drawbacks:
    * there is the chance of a race condition that a new preview is generated in the moment the folder is already migrated away - so the old folder with the newly cached preview is deleted and one cached preview needs to be re-generated
    * there is the chance of a race condition during access of a preview while it is migrated to the other folder - then no preview can be shown and results in a 404 (as of now this is an accepted risk)

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

3 files changed, 5 insertions, 3 deletions

diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 254840b3542..e29e8ce2e7b 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -829,6 +829,7 @@ return array(
     'OC\\Core\\Command\\Maintenance\\Repair' => $baseDir . '/core/Command/Maintenance/Repair.php',
     'OC\\Core\\Command\\Maintenance\\UpdateHtaccess' => $baseDir . '/core/Command/Maintenance/UpdateHtaccess.php',
     'OC\\Core\\Command\\Maintenance\\UpdateTheme' => $baseDir . '/core/Command/Maintenance/UpdateTheme.php',
+    'OC\\Core\\Command\\Preview\\Repair' => $baseDir . '/core/Command/Preview/Repair.php',
     'OC\\Core\\Command\\Security\\ImportCertificate' => $baseDir . '/core/Command/Security/ImportCertificate.php',
     'OC\\Core\\Command\\Security\\ListCertificates' => $baseDir . '/core/Command/Security/ListCertificates.php',
     'OC\\Core\\Command\\Security\\RemoveCertificate' => $baseDir . '/core/Command/Security/RemoveCertificate.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 45bf93241d5..8bb4f615520 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -858,6 +858,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OC\\Core\\Command\\Maintenance\\Repair' => __DIR__ . '/../../..' . '/core/Command/Maintenance/Repair.php',
         'OC\\Core\\Command\\Maintenance\\UpdateHtaccess' => __DIR__ . '/../../..' . '/core/Command/Maintenance/UpdateHtaccess.php',
         'OC\\Core\\Command\\Maintenance\\UpdateTheme' => __DIR__ . '/../../..' . '/core/Command/Maintenance/UpdateTheme.php',
+        'OC\\Core\\Command\\Preview\\Repair' => __DIR__ . '/../../..' . '/core/Command/Preview/Repair.php',
         'OC\\Core\\Command\\Security\\ImportCertificate' => __DIR__ . '/../../..' . '/core/Command/Security/ImportCertificate.php',
         'OC\\Core\\Command\\Security\\ListCertificates' => __DIR__ . '/../../..' . '/core/Command/Security/ListCertificates.php',
         'OC\\Core\\Command\\Security\\RemoveCertificate' => __DIR__ . '/../../..' . '/core/Command/Security/RemoveCertificate.php',
diff --git a/lib/private/Preview/Storage/Root.php b/lib/private/Preview/Storage/Root.php
index a9a72026a51..1f332c32085 100644
--- a/lib/private/Preview/Storage/Root.php
+++ b/lib/private/Preview/Storage/Root.php
@@ -39,7 +39,7 @@ class Root extends AppData {
 
 
 	public function getFolder(string $name): ISimpleFolder {
-		$internalFolder = $this->getInternalFolder($name);
+		$internalFolder = self::getInternalFolder($name);
 
 		try {
 			return parent::getFolder($internalFolder);
@@ -54,7 +54,7 @@ class Root extends AppData {
 	}
 
 	public function newFolder(string $name): ISimpleFolder {
-		$internalFolder = $this->getInternalFolder($name);
+		$internalFolder = self::getInternalFolder($name);
 		return parent::newFolder($internalFolder);
 	}
 
@@ -66,7 +66,7 @@ class Root extends AppData {
 		return [];
 	}
 
-	private function getInternalFolder(string $name): string {
+	public static function getInternalFolder(string $name): string {
 		return implode('/', str_split(substr(md5($name), 0, 7))) . '/' . $name;
 	}
 }