Handle file rescan (#2951)

* Fire handlers when file updated or moved
* Create galleries as needed
* Clean empty galleries
* Handle cleaning zip folders when path changed
* Fix gallery association on duplicate images
* Re-create missing folder-based galleries

pkg/txn/hooks.go

@@ -13,6 +13,7 @@ const (
 type hookManager struct {
 	postCommitHooks   []TxnFunc
 	postRollbackHooks []TxnFunc
+	postCompleteHooks []TxnFunc
 }
 
 func (m *hookManager) register(ctx context.Context) context.Context {
@@ -27,20 +28,26 @@ func hookManagerCtx(ctx context.Context) *hookManager {
 	return m
 }
 
-func executePostCommitHooks(ctx context.Context) {
-	m := hookManagerCtx(ctx)
-	for _, h := range m.postCommitHooks {
+func executeHooks(ctx context.Context, hooks []TxnFunc) {
+	for _, h := range hooks {
 		// ignore errors
 		_ = h(ctx)
 	}
 }
 
+func executePostCommitHooks(ctx context.Context) {
+	m := hookManagerCtx(ctx)
+	executeHooks(ctx, m.postCommitHooks)
+}
+
 func executePostRollbackHooks(ctx context.Context) {
 	m := hookManagerCtx(ctx)
-	for _, h := range m.postRollbackHooks {
-		// ignore errors
-		_ = h(ctx)
-	}
+	executeHooks(ctx, m.postRollbackHooks)
+}
+
+func executePostCompleteHooks(ctx context.Context) {
+	m := hookManagerCtx(ctx)
+	executeHooks(ctx, m.postCompleteHooks)
 }
 
 func AddPostCommitHook(ctx context.Context, hook TxnFunc) {
@@ -52,3 +59,8 @@ func AddPostRollbackHook(ctx context.Context, hook TxnFunc) {
 	m := hookManagerCtx(ctx)
 	m.postRollbackHooks = append(m.postRollbackHooks, hook)
 }
+
+func AddPostCompleteHook(ctx context.Context, hook TxnFunc) {
+	m := hookManagerCtx(ctx)
+	m.postCompleteHooks = append(m.postCompleteHooks, hook)
+}

pkg/txn/transaction.go

@@ -22,6 +22,11 @@ type TxnFunc func(ctx context.Context) error
 // WithTxn executes fn in a transaction. If fn returns an error then
 // the transaction is rolled back. Otherwise it is committed.
 func WithTxn(ctx context.Context, m Manager, fn TxnFunc) error {
+	const execComplete = true
+	return withTxn(ctx, m, fn, execComplete)
+}
+
+func withTxn(ctx context.Context, m Manager, fn TxnFunc, execCompleteOnLocked bool) error {
 	var err error
 	ctx, err = begin(ctx, m)
 	if err != nil {
@@ -38,10 +43,16 @@ func WithTxn(ctx context.Context, m Manager, fn TxnFunc) error {
 		if err != nil {
 			// something went wrong, rollback
 			rollback(ctx, m)
+
+			if execCompleteOnLocked || !m.IsLocked(err) {
+				executePostCompleteHooks(ctx)
+			}
 		} else {
 			// all good, commit
 			err = commit(ctx, m)
+			executePostCompleteHooks(ctx)
 		}
+
 	}()
 
 	err = fn(ctx)
@@ -102,7 +113,8 @@ func (r Retryer) WithTxn(ctx context.Context, fn TxnFunc) error {
 	var attempt int
 	var err error
 	for attempt = 1; attempt <= r.Retries || r.Retries < 0; attempt++ {
-		err = WithTxn(ctx, r.Manager, fn)
+		const execComplete = false
+		err = withTxn(ctx, r.Manager, fn, execComplete)
 
 		if err == nil {
 			return nil