better variable names in substitute_splits

Author: rnewson

src/fabric/src/fabric_drop_seq.erl

@@ -371,20 +371,20 @@ latest_shard_sync_checkpoints(ShardSyncHistory) ->
 -spec substitute_splits([#shard{}], uuid_map(), peer_checkpoints()) -> peer_checkpoints().
 substitute_splits(Shards, UuidMap, PeerCheckpoints) ->
     maps:fold(
-        fun({[B1, E1], Node}, {Uuid, Seq}, Acc) ->
+        fun({[PS, PE], Node}, {Uuid, Seq}, Acc) ->
             ShardsInRange = [
                 S
-             || #shard{range = [B2, E2]} = S <- Shards,
+             || #shard{range = [SS, SE]} = S <- Shards,
                 Node == S#shard.node,
-                B2 >= B1 andalso E2 =< E1
+                SS >= PS andalso SE =< PE
             ],
             %% lookup uuid from map if substituted
             AsMap = maps:from_list(
                 lists:filtermap(
                     fun(#shard{} = Shard) ->
                         Key = {Shard#shard.range, Shard#shard.node},
                         if
-                            [B1, E1] == Shard#shard.range ->
+                            [PS, PE] == Shard#shard.range ->
                                 {true, {Key, {Uuid, Seq}}};
                             true ->
                                 case maps:find(Key, UuidMap) of