Why isn't my !include directive working in MySQL?
When I created foo.cnf, I set the permissions to 777.  Apparently world-writable config files are ignored:
~/Workspace/project_time/mysql ()  $ mysql --print-defaults -uroot -p&lt;secret&gt; new_database;
mysql: [Warning] World-writable config file '/Users/myself/Workspace/project_time/mysql/foo.cnf' is ignored.
mysql would have been started with the following arguments:
--i_am_a_dummy -uroot -p&lt;secret&gt; new_database 

When I reset the permissions for foo.cnf to 755 and re-run the command, I get the following:
~/Workspace/project_time/mysql ()  $ chmod 755 foo.cnf 
~/Workspace/project_time/mysql ()  $ mysql --print-defaults -uroot -p&lt;secret&gt; new_database;
mysql would have been started with the following arguments:
--skip_column_names --i_am_a_dummy -uroot -p&lt;secret&gt; new_database 

And when I invoke the aforementioned SELECT statement in the CLI, it appears as expected:
mysql&gt; select * from t1;
+------+------+------+
| 2001 | 1    | 1    |
| 2001 | 1    | 20   |
| 2001 | 1    | 30   |
| 2001 | 2    | 2    |
| 2001 | 2    | 23   |
| 2001 | 2    | 23   |
+------+------+------+
6 rows in set (0.00 sec)

EDIT: The warning is actually printed out even when not passing the --print-defaults flag, I just didn't notice it among the other output in the CLI.  Since --print-defaults results in much less output on start-up, the warning was easier to notice.