cherry pick tikv#12251 to release-5.1

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

components/raftstore/src/store/peer.rs

@@ -848,7 +848,13 @@ where
             &mut kv_wb,
             &region,
             PeerState::Tombstone,
-            self.pending_merge_state.clone(),
+            // Only persist the `merge_state` if the merge is known to be succeeded
+            // which is determined by the `keep_data` flag
+            if keep_data {
+                self.pending_merge_state.clone()
+            } else {
+                None
+            },
         )?;
         // write kv rocksdb first in case of restart happen between two write
         let mut write_opts = WriteOptions::new();

components/test_raftstore/src/cluster.rs

@@ -1087,6 +1087,28 @@ impl<T: Simulator> Cluster<T> {
             .unwrap()
     }
 
+    pub fn must_peer_state(&self, region_id: u64, store_id: u64, peer_state: PeerState) {
+        for _ in 0..100 {
+            let state = self
+                .get_engine(store_id)
+                .c()
+                .get_msg_cf::<RegionLocalState>(
+                    engine_traits::CF_RAFT,
+                    &keys::region_state_key(region_id),
+                )
+                .unwrap()
+                .unwrap();
+            if state.get_state() == peer_state {
+                return;
+            }
+            sleep_ms(10);
+        }
+        panic!(
+            "[region {}] peer state still not reach {:?}",
+            region_id, peer_state
+        );
+    }
+
     pub fn wait_last_index(
         &mut self,
         region_id: u64,