Rework tab completion of COPY and \copy in psql

This corrects and simplifies $subject in a number of ways:
- Remove from the completion the pre-9.0 grammar still supported for
compatibility purposes.  This simplifies the code, and allows to extend
it more easily with new patterns.
- Add completion for the options of FORMAT within a WITH clause.
- Complete WHERE and WITH clauses correctly depending on if TO or FROM
are used, WHERE being only available with COPY FROM.

Author: Vignesh C, Michael Paquier
Reviewed-by: Ahsan Hadi
Discussion: https://postgr.es/m/CALDaNm3zWr=OmxeNqOqfT=uZTSdam_j-gkX94CL8eTNfgUtf6A@mail.gmail.com

src/bin/psql/tab-complete.c

@@ -2316,19 +2316,14 @@ psql_completion(const char *text, int start, int end)
 	else if (Matches("COPY|\\copy"))
 		COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_tables,
 								   " UNION ALL SELECT '('");
-	/* If we have COPY BINARY, complete with list of tables */
-	else if (Matches("COPY", "BINARY"))
-		COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_tables, NULL);
-	/* If we have COPY (, complete it with legal commands */
+	/* Complete COPY ( with legal query commands */
 	else if (Matches("COPY|\\copy", "("))
 		COMPLETE_WITH("SELECT", "TABLE", "VALUES", "INSERT", "UPDATE", "DELETE", "WITH");
-	/* If we have COPY [BINARY] <sth>, complete it with "TO" or "FROM" */
-	else if (Matches("COPY|\\copy", MatchAny) ||
-			 Matches("COPY", "BINARY", MatchAny))
+	/* Complete COPY <sth> */
+	else if (Matches("COPY|\\copy", MatchAny))
 		COMPLETE_WITH("FROM", "TO");
-	/* If we have COPY [BINARY] <sth> FROM|TO, complete with filename */
-	else if (Matches("COPY", MatchAny, "FROM|TO") ||
-			 Matches("COPY", "BINARY", MatchAny, "FROM|TO"))
+	/* Complete COPY <sth> FROM|TO with filename */
+	else if (Matches("COPY", MatchAny, "FROM|TO"))
 	{
 		completion_charp = "";
 		completion_force_quote = true;	/* COPY requires quoted filename */
@@ -2340,17 +2335,28 @@ psql_completion(const char *text, int start, int end)
 		completion_force_quote = false;
 		matches = rl_completion_matches(text, complete_from_files);
 	}
-	/* Offer options after COPY [BINARY] <sth> FROM|TO filename */
-	else if (Matches("COPY|\\copy", MatchAny, "FROM|TO", MatchAny) ||
-			 Matches("COPY", "BINARY", MatchAny, "FROM|TO", MatchAny))
-		COMPLETE_WITH("BINARY", "DELIMITER", "NULL", "CSV",
-					  "ENCODING");
-
-	/* Offer options after COPY [BINARY] <sth> FROM|TO filename CSV */
-	else if (Matches("COPY|\\copy", MatchAny, "FROM|TO", MatchAny, "CSV") ||
-			 Matches("COPY", "BINARY", MatchAny, "FROM|TO", MatchAny, "CSV"))
-		COMPLETE_WITH("HEADER", "QUOTE", "ESCAPE", "FORCE QUOTE",
-					  "FORCE NOT NULL");
+
+	/* Complete COPY <sth> TO <sth> */
+	else if (Matches("COPY|\\copy", MatchAny, "TO", MatchAny))
+		COMPLETE_WITH("WITH (");
+
+	/* Complete COPY <sth> FROM <sth> */
+	else if (Matches("COPY|\\copy", MatchAny, "FROM", MatchAny))
+		COMPLETE_WITH("WITH (", "WHERE");
+
+	/* Complete COPY <sth> FROM|TO filename WITH ( */
+	else if (Matches("COPY|\\copy", MatchAny, "FROM|TO", MatchAny, "WITH", "("))
+		COMPLETE_WITH("FORMAT", "FREEZE", "DELIMITER", "NULL",
+					  "HEADER", "QUOTE", "ESCAPE", "FORCE_QUOTE",
+					  "FORCE_NOT_NULL", "FORCE_NULL", "ENCODING");
+
+	/* Complete COPY <sth> FROM|TO filename WITH (FORMAT */
+	else if (Matches("COPY|\\copy", MatchAny, "FROM|TO", MatchAny, "WITH", "(", "FORMAT"))
+		COMPLETE_WITH("binary", "csv", "text");
+
+	/* Complete COPY <sth> FROM <sth> WITH (<options>) */
+	else if (Matches("COPY|\\copy", MatchAny, "FROM", MatchAny, "WITH", MatchAny))
+		COMPLETE_WITH("WHERE");
 
 	/* CREATE ACCESS METHOD */
 	/* Complete "CREATE ACCESS METHOD <name>" */