Improve tab completion of IMPORT FOREIGN SCHEMA in psql

It is not possible to get a list of foreign schemas as the server is not
known, so this provides instead a list of local schemas, which is more
useful than nothing if using a loopback server or having schema names
matching in the local and remote servers.

Author: Jeff Janes
Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/CAMkU=1wr7Roj41q-XiJs=Uyc2xCmHhcGGy7J-peJQK-e+w=ghw@mail.gmail.com

src/bin/psql/tab-complete.c

@@ -3293,6 +3293,17 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("FOREIGN SCHEMA");
 	else if (Matches("IMPORT", "FOREIGN"))
 		COMPLETE_WITH("SCHEMA");
+	else if (Matches("IMPORT", "FOREIGN", "SCHEMA", MatchAny))
+		COMPLETE_WITH("EXCEPT (", "FROM SERVER", "LIMIT TO (");
+	else if (TailMatches("LIMIT", "TO", "(*)") ||
+			 TailMatches("EXCEPT", "(*)"))
+		COMPLETE_WITH("FROM SERVER");
+	else if (TailMatches("FROM", "SERVER", MatchAny))
+		COMPLETE_WITH("INTO");
+	else if (TailMatches("FROM", "SERVER", MatchAny, "INTO"))
+		COMPLETE_WITH_QUERY(Query_for_list_of_schemas);
+	else if (TailMatches("FROM", "SERVER", MatchAny, "INTO", MatchAny))
+		COMPLETE_WITH("OPTIONS (");
 
 /* INSERT --- can be inside EXPLAIN, RULE, etc */
 	/* Complete INSERT with "INTO" */