Add reproduction program

repro.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+set -uex
+# Set POSTGRES_DIR and CITUS_DIR environment variables.
+
+pushd "$POSTGRES_DIR"
+git checkout REL9_5_3
+./configure --prefix=/tmp/pg --enable-cassert --enable-debug
+make -sj6 install
+popd
+
+
+pushd "$CITUS_DIR"
+PATH="/tmp/pg/bin:$PATH" ./configure
+make install && make -C src/test/regress check-multi || true # because it fails
+cat ./src/test/regress/tmp_check/master/log/postmaster.log
+# [...]
+# ERROR:  replication_factor must be positive
+# STATEMENT:  SELECT master_create_worker_shards('test_schema_support.nation_hash', 4, -1);
+# ERROR:  could not find any shards
+# DETAIL:  No shards exist for distributed table "nation_hash".
+# HINT:  Run master_create_worker_shards to create shards and try again.
+# STATEMENT:  INSERT INTO test_schema_support.nation_hash(n_nationkey, n_name, n_regionkey) VALUES (6, 'FRANCE', 3);
+# TRAP: BadArgument("!(shardId != 0)", File: "utils/resource_lock.c", Line: 75)
+# LOG:  server process (PID 32504) was terminated by signal 6: Aborted
+# DETAIL:  Failed process was running: SELECT * FROM test_schema_support.nation_hash WHERE n_nationkey = 6;
+# LOG:  terminating any other active server processes
+# WARNING:  terminating connection because of crash of another server process
+# DETAIL:  The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.
+# HINT:  In a moment you should be able to reconnect to the database and repeat your command
+# [...]
+popd
+