docs inaccuracy for MARIADB_DISABLE_UPGRADE_BACKUP

[mirekphd]

MariaDB docs (on Docker Hub here and at mariadb.com here) for MARIADB_DISABLE_UPGRADE_BACKUP are inaccurate (inconsistent with the current code):

Docs:

This backup process can be disabled with by setting MARIADB_DISABLE_UPGRADE_BACKUP to a non-empty value."

(e.g. https://hub.docker.com/_/mariadb)

vs. code:

{
	if [ -n "$MARIADB_DISABLE_UPGRADE_BACKUP" ] \
		&& [ "$MARIADB_DISABLE_UPGRADE_BACKUP" = 1 ]; then
		mysql_note "MariaDB upgrade backup disabled due to \$MARIADB_DISABLE_UPGRADE_BACKUP=1 setting"
		return

[ https://github.com/MariaDB/mariadb-docker/blob/master/docker-entrypoint.sh#L369 ]

Note also this issue, which affects multiple places (see list):

= and == are for string comparisons
-eq is for numeric comparisons

[ https://stackoverflow.com/a/20449556/9962007 ]

[martadinata666]

The problem here is "non empty value" , when usually we expect 1 as true, like MARIADB_AUTO_UPGRADE case. The #442 will result anything filled to the MARIADB_DISABLE_UPGRADE_BACKUP will be true. Imho, i prefer update documentation to set this ENV to 1 to enable this behaviour