Manual merge required.

mysql-test/r/mysql_client.result:
  manual merge
mysql-test/t/mysql_client.test:
  manual merge

mysql-test/r/mysql_client.result

@@ -2,3 +2,47 @@
 1
 ERROR 1064 (42000) at line 3: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
 ERROR at line 1: USE must be followed by a database name
+?         (\?) Synonym for `help'.
+clear     (\c) Clear command.
+connect   (\r) Reconnect to the server. Optional arguments are db and host.
+delimiter (\d) Set query delimiter. 
+edit      (\e) Edit command with $EDITOR.
+ego       (\G) Send command to mysql server, display result vertically.
+exit      (\q) Exit mysql. Same as quit.
+go        (\g) Send command to mysql server.
+help      (\h) Display this help.
+nopager   (\n) Disable pager, print to stdout.
+notee     (\t) Don't write into outfile.
+pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
+print     (\p) Print current command.
+prompt    (\R) Change your mysql prompt.
+quit      (\q) Quit mysql.
+rehash    (\#) Rebuild completion hash.
+source    (\.) Execute an SQL script file. Takes a file name as an argument.
+status    (\s) Get status information from the server.
+system    (\!) Execute a system shell command.
+tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
+use       (\u) Use another database. Takes database name as argument.
+charset_name(\C) Switch to another charset. Might be needed for processing binlog.
+?         (\?) Synonym for `help'.
+clear     (\c) Clear command.
+connect   (\r) Reconnect to the server. Optional arguments are db and host.
+delimiter (\d) Set query delimiter. 
+edit      (\e) Edit command with $EDITOR.
+ego       (\G) Send command to mysql server, display result vertically.
+exit      (\q) Exit mysql. Same as quit.
+go        (\g) Send command to mysql server.
+help      (\h) Display this help.
+nopager   (\n) Disable pager, print to stdout.
+notee     (\t) Don't write into outfile.
+pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
+print     (\p) Print current command.
+prompt    (\R) Change your mysql prompt.
+quit      (\q) Quit mysql.
+rehash    (\#) Rebuild completion hash.
+source    (\.) Execute an SQL script file. Takes a file name as an argument.
+status    (\s) Get status information from the server.
+system    (\!) Execute a system shell command.
+tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
+use       (\u) Use another database. Takes database name as argument.
+charset_name(\C) Switch to another charset. Might be needed for processing binlog.

mysql-test/t/mysql_client.test

@@ -27,3 +27,9 @@
 # client comment recognized, but parameter missing => error
 --exec echo "use"         >  $MYSQLTEST_VARDIR/tmp/bug20432.sql
 --exec $MYSQL              < $MYSQLTEST_VARDIR/tmp/bug20432.sql 2>&1
+
+#
+# Bug #20328: mysql client interprets commands in comments
+#
+--exec echo 'help' | $MYSQL
+--exec echo 'help ' | $MYSQL