MDEV-39061 mariadb-backup compatible wrappers for BACKUP SERVER

scripts/mariabackup/mariabackup.sh: a drop-in wrapper that lets
existing mariabackup invocations drive the server-side BACKUP
SERVER command without changing user scripts.

mariabackup.sh covers all four mariabackup modes. --backup
translates into "BACKUP SERVER TO '<dir>'" via the mariadb client,
forwarding connection options, and layers --stream/--compress as
tar/gzip pipelines on the result. --prepare runs mariadbd
--bootstrap on backup.cnf so InnoDB applies the archived redo log.
--copy-back / --move-back drop a prepared backup into the datadir
via cp -r / mv.

--prepare --incremental-dir copies the incremental's ib_logfile*
into the base and advances innodb_log_recovery_target;
innodb_log_recovery_start stays pinned to the base checkpoint.

--apply-log-only maps to --innodb-force-recovery=3 to skip
rollback between incrementals.

--rollback-xa runs two passes: normal recovery, then a second
bootstrap with --tc-heuristic-recover=ROLLBACK.

--copy-back / --move-back refuse a non-empty datadir unless
--force-non-empty-directories is set, and print the post-action
chown / systemctl start commands.

For incremental --backup, innodb_log_archive_start is treated as a
startup-only, read-only server invariant: the wrapper reads
@@global.innodb_log_archive_start and fails fast if the archive
floor exceeds the base backup's end LSN.

Limitations:
 --export is accepted but not yet implemented; the wrapper prints
a warning and runs plain recovery without producing the per-table
.cfg files needed for ALTER TABLE ... IMPORT TABLESPACE.

mbstream.sh shims the mbstream CLI onto tar, dropping
mbstream-only flags (-p/--parallel) so legacy pipelines keep
working.

README.md maps every supported option per mode to its BACKUP
SERVER equivalent and documents the backup.cnf format.

Add include/have_mariabackup_wrapper.inc redirects $XTRABACKUP to
the wrapper so a test opts in by sourcing one file; skips when the
wrapper, bash, or the mariadb client is unavailable.

wrapper_basic.test: exercises full backup, streaming, compression,
the ignored legacy options.

Author: Thirunarayanan

mysql-test/include/have_mariabackup_wrapper.inc

@@ -0,0 +1,56 @@
+# ==== Purpose ====
+#
+# Redirect `$XTRABACKUP` so existing test invocations like
+#
+#     --exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf \
+#         --backup --target-dir=$targetdir
+#
+# run through scripts/mariabackup/mariabackup.sh — the BACKUP SERVER
+# compatibility wrapper — without any change to the test body.
+#
+#
+# Skip the test if any of these are missing:
+#   - the wrapper script
+#   - bash
+#   - the mariadb client (wrapper shells out to it)
+#
+# ==== Usage ====
+#
+#   --source include/have_mariabackup_wrapper.inc
+#   # ... rest of the test, using $XTRABACKUP as usual ...
+#
+# ==== Exposed variables ====
+#
+#   $XTRABACKUP        — now points at mariabackup.sh
+
+--source include/linux.inc
+
+--let MARIABACKUP_WRAPPER=$MYSQL_TEST_DIR/../scripts/mariabackup/mariabackup.sh
+
+--error 0,1
+perl;
+use strict;
+use warnings;
+use File::Basename;
+
+my $wrapper = $ENV{MARIABACKUP_WRAPPER};
+exit 1 unless $wrapper && -x $wrapper;
+
+chomp(my $bash = `command -v bash 2>/dev/null`);
+exit 1 unless $bash && -x $bash;
+
+# Prepend its directory to PATH so the bare `mariadb` invocation
+# inside the wrapper resolves.
+my ($mariadb) = split /\s+/, ($ENV{MYSQL} // '');
+exit 1 unless $mariadb && -x $mariadb;
+$ENV{PATH} = dirname($mariadb) . ":$ENV{PATH}";
+
+exit 0;
+EOF
+
+if ($errno)
+{
+  --skip mariabackup.sh wrapper unavailable (script, bash, or mariadb client missing)
+}
+
+--let XTRABACKUP=$MARIABACKUP_WRAPPER

mysql-test/suite/mariabackup/wrapper_basic.result

@@ -0,0 +1,31 @@
+CREATE TABLE t1(a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1), (2), (3);
+#
+# Full backup succeeds and runs BACKUP SERVER
+#
+FOUND 1 /Executing: BACKUP SERVER TO/ in wrapper.log
+#
+# (--parallel/--throttle/--no-lock/--safe-slave-backup)
+#
+FOUND 1 /Executing: BACKUP SERVER TO/ in wrapper.log
+#
+# --stream=mbstream emits a valid tar archive to stdout
+#
+FOUND 1 /Creating tar stream/ in wrapper.log
+#
+# --compress produces a valid gzip stream
+#
+FOUND 1 /Compressing with gzip/ in wrapper.log
+#
+# Backup into an already-existing target directory is rejected
+#
+FOUND 1 /Target directory already exists/ in wrapper.log
+#
+# Missing --target-dir is rejected
+#
+FOUND 1 /--target-dir required/ in wrapper.log
+#
+# Non-existent parent directory is rejected
+#
+FOUND 1 /Parent directory does not exist/ in wrapper.log
+DROP TABLE t1;

mysql-test/suite/mariabackup/wrapper_basic.test

@@ -0,0 +1,82 @@
+--source include/have_mariabackup_wrapper.inc
+--source include/have_innodb.inc
+
+--let $defaults=--defaults-file=$MYSQLTEST_VARDIR/my.cnf
+--let $logfile=$MYSQLTEST_VARDIR/tmp/wrapper.log
+--let SEARCH_FILE=$logfile
+--let SEARCH_ABORT=NOT FOUND
+
+CREATE TABLE t1(a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1), (2), (3);
+
+--echo #
+--echo # Full backup succeeds and runs BACKUP SERVER
+--echo #
+--let $targetdir=$MYSQLTEST_VARDIR/tmp/bk_full
+--exec $XTRABACKUP $defaults --backup --target-dir=$targetdir > $logfile 2>&1
+--let SEARCH_PATTERN=Executing: BACKUP SERVER TO
+--source include/search_pattern_in_file.inc
+--rmdir $targetdir
+
+--echo #
+--echo # (--parallel/--throttle/--no-lock/--safe-slave-backup)
+--echo #
+--let $targetdir=$MYSQLTEST_VARDIR/tmp/bk_legacy
+--exec $XTRABACKUP $defaults --backup --target-dir=$targetdir --parallel=4 --throttle=100 --no-lock --safe-slave-backup > $logfile 2>&1
+--let SEARCH_PATTERN=Executing: BACKUP SERVER TO
+--source include/search_pattern_in_file.inc
+--rmdir $targetdir
+
+--echo #
+--echo # --stream=mbstream emits a valid tar archive to stdout
+--echo #
+--let $targetdir=$MYSQLTEST_VARDIR/tmp/bk_stream
+--let $streamfile=$MYSQLTEST_VARDIR/tmp/bk_stream.tar
+--exec $XTRABACKUP $defaults --backup --target-dir=$targetdir --stream=mbstream > $streamfile 2>$logfile
+--exec tar -tf $streamfile > /dev/null
+--let SEARCH_PATTERN=Creating tar stream
+--source include/search_pattern_in_file.inc
+--rmdir $targetdir
+--remove_file $streamfile
+
+--echo #
+--echo # --compress produces a valid gzip stream
+--echo #
+--let $targetdir=$MYSQLTEST_VARDIR/tmp/bk_gz
+--let $gzfile=$MYSQLTEST_VARDIR/tmp/bk.tar.gz
+--exec $XTRABACKUP $defaults --backup --target-dir=$targetdir --compress > $gzfile 2>$logfile
+--exec gzip -t $gzfile
+--let SEARCH_PATTERN=Compressing with gzip
+--source include/search_pattern_in_file.inc
+--rmdir $targetdir
+--remove_file $gzfile
+
+--echo #
+--echo # Backup into an already-existing target directory is rejected
+--echo #
+--let $targetdir=$MYSQLTEST_VARDIR/tmp/bk_exists
+--mkdir $targetdir
+--error 1
+--exec $XTRABACKUP $defaults --backup --target-dir=$targetdir > $logfile 2>&1
+--let SEARCH_PATTERN=Target directory already exists
+--source include/search_pattern_in_file.inc
+--rmdir $targetdir
+
+--echo #
+--echo # Missing --target-dir is rejected
+--echo #
+--error 1
+--exec $XTRABACKUP $defaults --backup > $logfile 2>&1
+--let SEARCH_PATTERN=--target-dir required
+--source include/search_pattern_in_file.inc
+
+--echo #
+--echo # Non-existent parent directory is rejected
+--echo #
+--error 1
+--exec $XTRABACKUP $defaults --backup --target-dir=$MYSQLTEST_VARDIR/tmp/no_such_parent/bk > $logfile 2>&1
+--let SEARCH_PATTERN=Parent directory does not exist
+--source include/search_pattern_in_file.inc
+
+DROP TABLE t1;
+--remove_file $logfile