feat: Allow manually specifying event IDs as extremities

src/admin/debug/commands.rs

@@ -920,3 +920,49 @@ pub(super) async fn trim_memory(&self) -> Result {
 
 	writeln!(self, "done").await
 }
+
+#[admin_command]
+pub(super) async fn force_append_latest_extremity(
+	&self,
+	room_id: OwnedRoomId,
+	event_id: Option<OwnedEventId>,
+) -> Result {
+	let lock = self.services.rooms.state.mutex.lock(&*room_id).await;
+	let mut extremities: Vec<&EventId> = self
+		.services
+		.rooms
+		.state
+		.get_forward_extremities(&room_id)
+		.collect()
+		.await;
+
+	let selected_id = if let Some(event_id) = event_id {
+		event_id
+	} else {
+		self.services
+			.rooms
+			.timeline
+			.latest_pdu_in_room(&room_id)
+			.await
+			.map_err(|_| err!(Database("Failed to find the latest PDU in database")))?
+			.event_id()
+			.to_owned()
+	};
+
+	if !extremities.contains(&selected_id.as_ref()) {
+		extremities.push(&selected_id);
+	}
+
+	self.services
+		.rooms
+		.state
+		.set_forward_extremities(&room_id, extremities.iter().copied(), &lock)
+		.await;
+
+	self.write_str(&format!(
+		"Successfully retained the following {} forward extremities in room \
+		 {room_id}:\n```\n{extremities:?}\n```",
+		extremities.len()
+	))
+	.await
+}

src/admin/debug/mod.rs

@@ -237,6 +237,16 @@ pub enum DebugCommand {
 		level: Option<i32>,
 	},
 
+	/// - Forcefully add the latest known event in the specified room as a
+	///   forward extremity. Use with caution.
+	ForceAppendLatestExtremity {
+		/// The room ID
+		room_id: OwnedRoomId,
+		/// If set, forcefully picks an event ID to use as an extremity. Is not
+		/// validated.
+		event_id: Option<OwnedEventId>,
+	},
+
 	/// - Developer test stubs
 	#[command(subcommand)]
 	#[allow(non_snake_case)]