tab completion for extension versions

diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
new file mode 100644
index 1619de5..4eb5058
*** a/src/bin/psql/tab-complete.c
--- b/src/bin/psql/tab-complete.c
*************** static const SchemaQuery Query_for_list_
*** 729,734 ****
--- 729,741 ----
  "   FROM pg_catalog.pg_available_extensions "\
  "  WHERE substring(pg_catalog.quote_ident(name),1,%d)='%s' AND installed_version IS NULL"
  
+ /* the silly-looking length condition is just to eat up the current word */
+ #define Query_for_list_of_available_extension_versions \
+ " SELECT pg_catalog.quote_ident(version) "\
+ "   FROM pg_catalog.pg_available_extension_versions "\
+ "  WHERE (%d = pg_catalog.length('%s'))"\
+ "    AND pg_catalog.quote_ident(name)='%s'"
+ 
  #define Query_for_list_of_prepared_statements \
  " SELECT pg_catalog.quote_ident(name) "\
  "   FROM pg_catalog.pg_prepared_statements "\
*************** psql_completion(const char *text, int st
*** 2266,2275 ****
  			 pg_strcasecmp(prev2_wd, "EXTENSION") == 0)
  	{
  		static const char *const list_CREATE_EXTENSION[] =
! 		{"WITH SCHEMA", "CASCADE", NULL};
  
  		COMPLETE_WITH_LIST(list_CREATE_EXTENSION);
  	}
  
  	/* CREATE FOREIGN */
  	else if (pg_strcasecmp(prev2_wd, "CREATE") == 0 &&
--- 2273,2290 ----
  			 pg_strcasecmp(prev2_wd, "EXTENSION") == 0)
  	{
  		static const char *const list_CREATE_EXTENSION[] =
! 		{"WITH SCHEMA", "CASCADE", "VERSION", NULL};
  
  		COMPLETE_WITH_LIST(list_CREATE_EXTENSION);
  	}
+ 	/* CREATE EXTENSION <name> VERSION */
+ 	else if (pg_strcasecmp(prev4_wd, "CREATE") == 0 &&
+ 			 pg_strcasecmp(prev3_wd, "EXTENSION") == 0 &&
+ 			 pg_strcasecmp(prev_wd, "VERSION") == 0)
+ 	{
+ 		completion_info_charp = prev2_wd;
+ 		COMPLETE_WITH_QUERY(Query_for_list_of_available_extension_versions);
+ 	}
  
  	/* CREATE FOREIGN */
  	else if (pg_strcasecmp(prev2_wd, "CREATE") == 0 &&