MDEV-6137 better help for SET/ENUM sysvars

Auto-generate the allowed list of values for enum/set/flagset options
in --help output. But don't do that when the help text already has them.

Also, remove lists of values from help strings of various options, where
they were simply listed without any additional information.

mysql-test/r/mysqld--help.result

@@ -39,8 +39,7 @@ The following options may be given as the first argument:
  increase this to get more performance
  --binlog-checksum=name 
  Type of BINLOG_CHECKSUM_ALG. Include checksum for log
- events in the binary log. Possible values are NONE and
- CRC32; default is NONE.
+ events in the binary log. One of: NONE, CRC32
  --binlog-commit-wait-count=# 
  If non-zero, binlog write will wait at most
  binlog_commit_wait_usec microseconds for at least this
@@ -71,10 +70,7 @@ The following options may be given as the first argument:
  statements where only row-based is correct: those which
  involve user-defined functions (i.e. UDFs) or the UUID()
  function; for those, row-based binary logging is
- automatically used. If NDBCLUSTER is enabled and
- binlog-format is MIXED, the format switches to row-based
- and back implicitly per each query accessing an
- NDBCLUSTER table
+ automatically used.
  --binlog-ignore-db=name 
  Tells the master that updates to the given database
  should not be logged to the binary log.
@@ -114,11 +110,11 @@ The following options may be given as the first argument:
  --collation-server=name 
  Set the default collation.
  --completion-type=name 
- The transaction completion type, one of NO_CHAIN, CHAIN,
+ The transaction completion type. One of: NO_CHAIN, CHAIN,
  RELEASE
  --concurrent-insert[=name] 
- Use concurrent insert with MyISAM. Possible values are
- NEVER, AUTO, ALWAYS
+ Use concurrent insert with MyISAM. One of: NEVER, AUTO, 
+ ALWAYS
  --console           Write error output on screen; don't remove the console
  window on windows.
  --core-file         Write core on errors.
@@ -137,9 +133,8 @@ The following options may be given as the first argument:
  Short timeout for the two-step deadlock detection (in
  microseconds)
  --default-regex-flags=name 
- Default flags for the regex library. Syntax:
- default-regex-flags='[flag[,flag[,flag...]]]'. See the
- manual for the complete list of valid flags
+ Default flags for the regex library. Any combination of: 
+ DOTALL, DUPNAMES, EXTENDED, EXTRA, MULTILINE, UNGREEDY
  --default-storage-engine=name 
  The default storage engine for new tables
  --default-time-zone=name 
@@ -150,7 +145,7 @@ The following options may be given as the first argument:
  --default-week-format=# 
  The default week format used by WEEK() functions
  --delay-key-write[=name] 
- Type of DELAY_KEY_WRITE
+ Type of DELAY_KEY_WRITE. One of: OFF, ON, ALL
  --delayed-insert-limit=# 
  After inserting delayed_insert_limit rows, the INSERT
  DELAYED handler will check if there are any SELECT
@@ -252,7 +247,7 @@ The following options may be given as the first argument:
  (unless the user has SUPER privilege)
  --init-file=name    Read SQL commands from this file at startup
  --init-rpl-role=name 
- Set the replication role.
+ Set the replication role. One of: MASTER, SLAVE
  --init-slave=name   Command(s) that are executed by a slave server each time
  the SQL thread starts
  --interactive-timeout=# 
@@ -329,8 +324,8 @@ The following options may be given as the first argument:
  not specified then 'datadir'/'log-basename'.err or the
  'pid-file' path with extension .err is used
  --log-isam[=name]   Log all MyISAM changes to file.
- --log-output=name   Syntax: log-output=value[,value...], where "value" could
- be TABLE, FILE or NONE
+ --log-output=name   How logs should be written. Any combination of: NONE, 
+ FILE, TABLE
  --log-queries-not-using-indexes 
  Log queries that are executed without benefit of any
  index to the slow log if it is open
@@ -343,10 +338,9 @@ The following options may be given as the first argument:
  Log slow OPTIMIZE, ANALYZE, ALTER and other
  administrative statements to the slow log if it is open.
  --log-slow-filter=name 
- Log only certain types of queries. Multiple flags can be
- specified, separated by commas. Valid values are admin,
- slave, filesort, filesort_on_disk, full_join, full_scan,
- query_cache, query_cache_miss, tmp_table,
+ Log only certain types of queries. Any combination of: 
+ admin, filesort, filesort_on_disk, full_join, full_scan, 
+ query_cache, query_cache_miss, tmp_table, 
  tmp_table_on_disk
  --log-slow-rate-limit=# 
  Write to slow log every #th slow query. Set to 1 to log
@@ -356,8 +350,8 @@ The following options may be given as the first argument:
  Log slow statements executed by slave thread to the slow
  log if it is open.
  --log-slow-verbosity=name 
- log-slow-verbosity=[value[,value ...]] where value is one
- of 'innodb', 'query_plan', 'explain' 
+ Verbosity level for the slow log. Any combination of: 
+ innodb, query_plan, explain
  --log-tc=name       Path to transaction coordinator log (used for
  transactions that affect more than one storage engine,
  when binary log is disabled).
@@ -458,9 +452,9 @@ The following options may be given as the first argument:
  Restricts the total memory used for memory mapping of
  MySQL tables
  --myisam-recover-options[=name] 
- Syntax: myisam-recover-options[=option[,option...]],
- where option can be DEFAULT, BACKUP, BACKUP_ALL, FORCE,
- QUICK, or OFF
+ Specifies how corrupted tables should be automatically
+ repaired. Any combination of: DEFAULT, BACKUP, FORCE, 
+ QUICK, BACKUP_ALL, OFF
  --myisam-repair-threads=# 
  If larger than 1, when repairing a MyISAM table all
  indexes will be created in parallel, with one thread per
@@ -489,8 +483,9 @@ The following options may be given as the first argument:
  See also --old-mode
  --old-alter-table   Use old, non-optimized alter table
  --old-mode=name     Used to emulate old behavior from earlier MariaDB or
- MySQL versions. Syntax: old_mode=mode[,mode[,mode...]].
- See the manual for the complete list of valid old modes
+ MySQL versions. Any combination of: 
+ NO_DUP_KEY_WARNINGS_WITH_IGNORE, NO_PROGRESS_INFO, 
+ ZERO_DATE_TIME_CAST
  --old-passwords     Use old password encryption method (needed for 4.0 and
  older clients)
  --old-style-user-limits 
@@ -524,19 +519,20 @@ The following options may be given as the first argument:
  Controls number of record samples to check condition
  selectivity
  --optimizer-switch=name 
- optimizer_switch=option=val[,option=val...], where option
- is one of {derived_merge, derived_with_keys, firstmatch,
- in_to_exists, engine_condition_pushdown,
- index_condition_pushdown, index_merge,
- index_merge_intersection, index_merge_sort_intersection,
- index_merge_sort_union, index_merge_union,
- join_cache_bka, join_cache_hashed,
- join_cache_incremental, loosescan, materialization, mrr,
- mrr_cost_based, mrr_sort_keys, optimize_join_buffer_size,
- outer_join_with_cache, partial_match_rowid_merge,
- partial_match_table_scan, semijoin, semijoin_with_cache,
- subquery_cache, table_elimination, extended_keys,
- exists_to_in } and val is one of {on, off, default}
+ Fine-tune the optimizer behavior. Takes a comma-separated
+ list of option=value pairs, where value is on, off, or
+ default, and options are: index_merge, index_merge_union,
+ index_merge_sort_union, index_merge_intersection, 
+ index_merge_sort_intersection, engine_condition_pushdown,
+ index_condition_pushdown, derived_merge, 
+ derived_with_keys, firstmatch, loosescan, materialization,
+ in_to_exists, semijoin, partial_match_rowid_merge, 
+ partial_match_table_scan, subquery_cache, mrr, 
+ mrr_cost_based, mrr_sort_keys, outer_join_with_cache, 
+ semijoin_with_cache, join_cache_incremental, 
+ join_cache_hashed, join_cache_bka, 
+ optimize_join_buffer_size, table_elimination, 
+ extended_keys, exists_to_in
  --optimizer-use-condition-selectivity=# 
  Controls selectivity of which conditions the optimizer
  takes into account to calculate cardinality of a partial
@@ -689,9 +685,9 @@ The following options may be given as the first argument:
  in an incremental way. It can be specified many times,
  adding more plugins every time.
  --plugin-maturity=name 
- The lowest desirable plugin maturity (unknown,
- experimental, alpha, beta, gamma, or stable). Plugins
- less mature than that will not be installed or loaded.
+ The lowest desirable plugin maturity. Plugins less mature
+ than that will not be installed or loaded. One of: 
+ unknown, experimental, alpha, beta, gamma, stable
  -P, --port=#        Port number to use for connection or 0 to default to,
  my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default
  (3306), whatever comes first
@@ -934,11 +930,10 @@ The following options may be given as the first argument:
  transaction in case it failed with a deadlock or elapsed
  lock wait timeout, before giving up and stopping
  --slave-type-conversions=name 
- Set of slave type conversions that are enabled. Legal
- values are: ALL_LOSSY to enable lossy conversions and
- ALL_NON_LOSSY to enable non-lossy conversions. If the
- variable is assigned the empty set, no conversions are
- allowed and it is expected that the types match exactly.
+ Set of slave type conversions that are enabled. If the
+ variable is empty, no conversions are allowed and it is
+ expected that the types match exactly. Any combination
+ of: ALL_LOSSY, ALL_NON_LOSSY
  --slow-launch-time=# 
  If creating the thread takes longer than this value (in
  seconds), the Slow_launch_threads counter will be
@@ -955,8 +950,18 @@ The following options may be given as the first argument:
  --sort-buffer-size=# 
  Each thread that needs to do a sort allocates a buffer of
  this size
- --sql-mode=name     Syntax: sql-mode=mode[,mode[,mode...]]. See the manual
- for the complete list of valid sql modes
+ --sql-mode=name     Sets the sql mode. Any combination of: REAL_AS_FLOAT, 
+ PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, 
+ IGNORE_BAD_TABLE_OPTIONS, ONLY_FULL_GROUP_BY, 
+ NO_UNSIGNED_SUBTRACTION, NO_DIR_IN_CREATE, POSTGRESQL, 
+ ORACLE, MSSQL, DB2, MAXDB, NO_KEY_OPTIONS, 
+ NO_TABLE_OPTIONS, NO_FIELD_OPTIONS, MYSQL323, MYSQL40, 
+ ANSI, NO_AUTO_VALUE_ON_ZERO, NO_BACKSLASH_ESCAPES, 
+ STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE, 
+ NO_ZERO_DATE, ALLOW_INVALID_DATES, 
+ ERROR_FOR_DIVISION_BY_ZERO, TRADITIONAL, 
+ NO_AUTO_CREATE_USER, HIGH_NOT_PRECEDENCE, 
+ NO_ENGINE_SUBSTITUTION, PAD_CHAR_TO_FULL_LENGTH
  --stack-trace       Print a symbolic stack trace on failure
  (Defaults to on; use --skip-stack-trace to disable.)
  --stored-program-cache=# 
@@ -987,8 +992,8 @@ The following options may be given as the first argument:
  --table-open-cache=# 
  The number of cached open tables
  --tc-heuristic-recover=name 
- Decision to use in heuristic recover process. Possible
- values are COMMIT or ROLLBACK.
+ Decision to use in heuristic recover process. One of: 
+ COMMIT, ROLLBACK
  --thread-cache-size=# 
  How many threads we should keep in a cache for reuse
  --thread-pool-idle-timeout=# 
@@ -1024,7 +1029,9 @@ The following options may be given as the first argument:
  Allocation block size for transactions to be stored in
  binary log
  --transaction-isolation=name 
- Default transaction isolation level.
+ Default transaction isolation level. One of: 
+ READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, 
+ SERIALIZABLE
  --transaction-prealloc-size=# 
  Persistent buffer for transactions to be stored in binary
  log
@@ -1039,8 +1046,8 @@ The following options may be given as the first argument:
  of the underlying table and the query uses a LIMIT clause
  (usually get from GUI tools)
  --use-stat-tables=name 
- Specifies how to use system statistics tables. Possible
- values are NEVER, COMPLEMENTARY, PREFERABLY
+ Specifies how to use system statistics tables. One of: 
+ NEVER, COMPLEMENTARY, PREFERABLY
  -u, --user=name     Run mysqld daemon as user.
  --userstat          Enables statistics gathering for USER_STATISTICS,
  CLIENT_STATISTICS, INDEX_STATISTICS and TABLE_STATISTICS
@@ -1196,7 +1203,7 @@ myisam-mmap-size 18446744073709551615
 myisam-recover-options DEFAULT
 myisam-repair-threads 1
 myisam-sort-buffer-size 134216704
-myisam-stats-method nulls_unequal
+myisam-stats-method NULLS_UNEQUAL
 myisam-use-mmap FALSE
 net-buffer-length 16384
 net-read-timeout 30
@@ -1282,7 +1289,7 @@ relay-log-purge TRUE
 relay-log-recovery FALSE
 relay-log-space-limit 0
 replicate-annotate-row-events FALSE
-replicate-events-marked-for-skip replicate
+replicate-events-marked-for-skip REPLICATE
 replicate-same-server-id FALSE
 report-host (No default value)
 report-password (No default value)