Bug #4004 ALTER TABLE bla auto_increment=something' affects the value of the primary key

Description:
1) I have a table that is being created with this script:

DROP TABLE IF EXISTS `artists`;
CREATE TABLE `artists` (
  `artist_id` int(11) NOT NULL auto_increment,
  `artist` varchar(100) default NULL,
  `firstLetter` char(1) NOT NULL default '#',
  `mask` VARCHAR(100),
  `regex` VARCHAR(255),
  PRIMARY KEY  (`artist_id`),
  KEY `artist` (`artist`(20)),
  KEY `firstletter` (`firstLetter`)
) TYPE=MyISAM;
ALTER TABLE artists auto_increment=0;
INSERT INTO artists VALUES("0","Unknown","U", "Unknown", "^Unknown$");
UPDATE artists SET artist_id=0;

It is important for me to have the first record with the primary key == 0

Then I add some records to the table and want to change the auto_increment:

INSERT INTO artists SET artist = "XXX";
INSERT INTO artists SET artist = "YYY";

ALTER TABLE artists auto_increment=99999;

INSERT INTO artists SET artist = "ZZZ";

I find that the value of the primary key in the first record was changed:

99999,Unknown,U,Unknown,^Unknown$
2,XXX,#,NULL,NULL
3,YYY,#,NULL,NULL
100000,ZZZ,#,NULL,NULL

It was expected that Unknown has the value of 0; 

How to repeat:
simply run this in MySQL-Front or something:

DROP TABLE IF EXISTS `artists`;
CREATE TABLE `artists` (
  `artist_id` int(11) NOT NULL auto_increment,
  `artist` varchar(100) default NULL,
  `firstLetter` char(1) NOT NULL default '#',
  `mask` VARCHAR(100),
  `regex` VARCHAR(255),
  PRIMARY KEY  (`artist_id`),
  KEY `artist` (`artist`(20)),
  KEY `firstletter` (`firstLetter`)
) TYPE=MyISAM;
ALTER TABLE artists auto_increment=0;
INSERT INTO artists VALUES("0","Unknown","U", "Unknown", "^Unknown$");
UPDATE artists SET artist_id=0;

INSERT INTO artists SET artist = "XXX";
INSERT INTO artists SET artist = "YYY";

ALTER TABLE artists auto_increment=99999;

INSERT INTO artists SET artist = "ZZZ";
SELECT * FROM artists

You will have:

99999,Unknown,U,Unknown,^Unknown$
2,XXX,#,NULL,NULL
3,YYY,#,NULL,NULL
100000,ZZZ,#,NULL,NULL

Then Run this 

simply run this in MySQL-Front or something:

DROP TABLE IF EXISTS `artists`;
CREATE TABLE `artists` (
  `artist_id` int(11) NOT NULL auto_increment,
  `artist` varchar(100) default NULL,
  `firstLetter` char(1) NOT NULL default '#',
  `mask` VARCHAR(100),
  `regex` VARCHAR(255),
  PRIMARY KEY  (`artist_id`),
  KEY `artist` (`artist`(20)),
  KEY `firstletter` (`firstLetter`)
) TYPE=MyISAM;
ALTER TABLE artists auto_increment=0;
INSERT INTO artists VALUES("0","Unknown","U", "Unknown", "^Unknown$");
UPDATE artists SET artist_id=0;

INSERT INTO artists SET artist = "XXX";
INSERT INTO artists SET artist = "YYY";

SELECT * FROM artists

artist_id,artist,firstLetter,mask,regex
0,Unknown,U,Unknown,^Unknown$
2,XXX,#,NULL,NULL
3,YYY,#,NULL,NULL

Suggested fix:
Check what happens when the 'auto_increment = something' command is run.

in 4.0, auto_increment columns automatically generate a new value when given a 0.  Your ALTER TABLE to modify the auto_increment is causing it to generate a new value (hence the 99999 for the row you set to 0).

4.1 has support for the sql_mode NO_AUTO_VALUE_ON_ZERO which can disable this; see the SQL Mode chapter and the CREATE TABLE Syntax chapter for comments about this.