Sqlcmd doesn't validate custom batch separator

[shueybubbles]

The ODBC sqlcmd disallows a batch separator that matches any value in this list. go-sqlcmd probably should do so.

BACKUP,BREAK,BROWSE,BULK,CHECKPOINT,CLUSTERED,COMMITTED,COMPUTE,CONFIRM,CONTROLROW,DATABASE,DBCC,DISK,DISTRIBUTED,DUMMY,ERRLVL,ERROREXIT,EXIT,FILE,FILLFACTOR,FLOPPY,HOLDLOCK,IDENTITY_INSERT,IDENTITYCOL,IF,KILL,LINENO,MERGE,MIRROREXIT,NONCLUSTERED,OFF,OFFSETS,ONCE,OVER,PERCENT,PERM,PERMANENT,PLAN,PRINT,PROC,PROCESSEXIT,RAISERROR,READ,READTEXT,RECONFIGURE,REPEATABLE,RESTORE,RETURN,ROWCOUNT,RULE,SAVE,SERIALIZABLE,SETUSER,SHUTDOWN,STATISTICS,TAPE,TEMP,TEXTSIZE,TOP,TRAN,TRIGGER,TRUNCATE,TSEQUEL,UNCOMMITTED,UPDATETEXT,USE,WAITFOR,WHILE,WRITETEXT

[shueybubbles]

I think the best we can do is pick one of the lists from here, and try to update it occasionally:

https://docs.microsoft.com/en-us/sql/t-sql/language-elements/reserved-keywords-transact-sql?redirectedfrom=MSDN&view=sql-server-ver15