feat: move the messages only from INBOX and Spam folders

We do not try to delete resent messages
anymore. Previously resent messages
were distinguised by having duplicate Message-ID,
but future Date, but now we need to download
the message before we even see the Date.
We now move the message to the destination folder
but do not fetch it.

It may not be a good idea to delete
the duplicate in multi-device setups anyway,
because the device which has a message
may delete the duplicate of a message
the other device missed.

To avoid triggering IMAP busy move loop
described in the comments
we now only move the messages
from INBOX and Spam folders.

python/tests/test_1_online.py

@@ -308,7 +308,7 @@ def test_move_works(acfactory):
 
 
 def test_move_avoids_loop(acfactory):
-    """Test that the message is only moved once.
+    """Test that the message is only moved from INBOX to DeltaChat.
 
     This is to avoid busy loop if moved message reappears in the Inbox
     or some scanned folder later.
@@ -319,6 +319,14 @@ def test_move_avoids_loop(acfactory):
     ac1 = acfactory.new_online_configuring_account()
     ac2 = acfactory.new_online_configuring_account(mvbox_move=True)
     acfactory.bring_accounts_online()
+
+    # Create INBOX.DeltaChat folder and make sure
+    # it is detected by full folder scan.
+    ac2.direct_imap.create_folder("INBOX.DeltaChat")
+    ac2.stop_io()
+    ac2.start_io()
+    ac2._evtracker.get_info_contains("Found folders:")  #  Wait until the end of folder scan.
+
     ac1_chat = acfactory.get_accepted_chat(ac1, ac2)
     ac1_chat.send_text("Message 1")
 
@@ -326,20 +334,28 @@ def test_move_avoids_loop(acfactory):
     ac2_msg1 = ac2._evtracker.wait_next_incoming_message()
     assert ac2_msg1.text == "Message 1"
 
-    # Move the message to the INBOX again.
+    # Move the message to the INBOX.DeltaChat again.
+    # We assume that test server uses "." as the delimiter.
     ac2.direct_imap.select_folder("DeltaChat")
-    ac2.direct_imap.conn.move(["*"], "INBOX")
+    ac2.direct_imap.conn.move(["*"], "INBOX.DeltaChat")
 
     ac1_chat.send_text("Message 2")
     ac2_msg2 = ac2._evtracker.wait_next_incoming_message()
     assert ac2_msg2.text == "Message 2"
 
-    # Check that Message 1 is still in the INBOX folder
+    # Stop and start I/O to trigger folder scan.
+    ac2.stop_io()
+    ac2.start_io()
+    ac2._evtracker.get_info_contains("Found folders:")  #  Wait until the end of folder scan.
+
+    # Check that Message 1 is still in the INBOX.DeltaChat folder
     # and Message 2 is in the DeltaChat folder.
     ac2.direct_imap.select_folder("INBOX")
-    assert len(ac2.direct_imap.get_all_messages()) == 1
+    assert len(ac2.direct_imap.get_all_messages()) == 0
     ac2.direct_imap.select_folder("DeltaChat")
     assert len(ac2.direct_imap.get_all_messages()) == 1
+    ac2.direct_imap.select_folder("INBOX.DeltaChat")
+    assert len(ac2.direct_imap.get_all_messages()) == 1
 
 
 def test_move_works_on_self_sent(acfactory):
@@ -450,14 +466,19 @@ def test_resend_message(acfactory, lp):
     lp.sec("ac2: receive message")
     msg_in = ac2._evtracker.wait_next_incoming_message()
     assert msg_in.text == "message"
-    chat2 = msg_in.chat
-    chat2_msg_cnt = len(chat2.get_messages())
 
     lp.sec("ac1: resend message")
     ac1.resend_messages([msg_in])
 
-    lp.sec("ac2: check that message is deleted")
-    ac2._evtracker.get_matching("DC_EVENT_IMAP_MESSAGE_DELETED")
+    lp.sec("ac1: send another message")
+    chat1.send_text("another message")
+
+    lp.sec("ac2: receive another message")
+    msg_in = ac2._evtracker.wait_next_incoming_message()
+    assert msg_in.text == "another message"
+    chat2 = msg_in.chat
+    chat2_msg_cnt = len(chat2.get_messages())
+
     assert len(chat2.get_messages()) == chat2_msg_cnt
 
 
@@ -1757,10 +1778,10 @@ def test_group_quote(acfactory, lp):
             "xyz",
         ),  # Test that emails aren't found in a random folder
         (
-            "Spam",
+            "xyz",
             True,
-            "DeltaChat",
-        ),  # ...emails are moved from the spam folder to "DeltaChat"
+            "xyz",
+        ),  # ...emails are found in a random folder and downloaded without moving
         (
             "Spam",
             False,