imap: do not unnecessarily SELECT folder in move_delete_messages()

If there are no MOVE/DELETE operations pending, the folder
should not be SELECTed.

When `only_fetch_mvbox` is enabled, `fetch_new_messages` skips
most folders, but `move_delete_messages` always selects the
folder even if there are no operations pending. Selecting
all folders wastes time during folder scan and turns
recent messages into non-recent.

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+- do not unnecessarily SELECT folders if there are no operations planned on
+  them #3333
+
+
 ## 1.83.0
 
 ### Fixes

src/imap.rs

@@ -1030,9 +1030,14 @@ impl Imap {
             .await?;
 
         self.prepare(context).await?;
-        self.select_folder(context, Some(folder)).await?;
 
         for (target, rowid_set, uid_set) in UidGrouper::from(rows) {
+            // Select folder inside the loop to avoid selecting it if there are no pending
+            // MOVE/DELETE operations. This does not result in multiple SELECT commands
+            // being sent because `select_folder()` does nothing if the folder is already
+            // selected.
+            self.select_folder(context, Some(folder)).await?;
+
             // Empty target folder name means messages should be deleted.
             if target.is_empty() {
                 self.delete_message_batch(context, &uid_set, rowid_set)