error_if_data_home_dir() fails to detect trailing '/'

# BACKUP SERVER TO a data directory subdirectory spelled with '/./' and ending in '/' is accepted.

# Without the trailing '/', the same target is refused. Other non-canonical spellings such as '//' behave the same.

--error 0,ER_WRONG_ARGUMENTS

--evalp BACKUP SERVER TO '/.$MARIADB_DATADIR/bk/'

if (!$mysql_errno)

{

  --rmdir $MARIADB_DATADIR/bk

  --die A backup was written into the data directory because the target path ended in a slash

}