Bug #49837 mysqltest exec cannot handle multi-line command correctly

Since the exec command line is passed on externally, it cannot take newlines
Simply replace \n with space
Now also added test case

client/mysqltest.cc

@@ -2661,6 +2661,10 @@ void do_exec(struct st_command *command)
 #endif
 #endif
 
+  /* exec command is interpreted externally and will not take newlines */
+  while(replace(&ds_cmd, "\n", 1, " ", 1) == 0)
+    ;
+  
   DBUG_PRINT("info", ("Executing '%s' as '%s'",
                       command->first_argument, ds_cmd.str));
 

mysql-test/r/mysqltest.result

@@ -216,6 +216,12 @@ source database
 echo message echo message
 
 mysqltest: At line 1: Missing argument in exec
+1
+1
+2
+2
+X
+3
 MySQL
 "MySQL"
 MySQL: The

mysql-test/t/mysqltest.test

@@ -605,6 +605,15 @@ echo ;
 --error 1
 --exec echo "--exec " | $MYSQL_TEST 2>&1
 
+# Multi-line exec
+exec $MYSQL
+    test -e "select 1";
+exec $MYSQL test -e "select
+    2";
+let $query = select 3
+    as X;
+exec $MYSQL test -e "$query";
+
 # ----------------------------------------------------------------------------
 # Test let command
 # ----------------------------------------------------------------------------