LP #1417214: Plugin hooks for pt-table-checksum need to be expanded

**Reported in Launchpad by Joe last update 23-02-2015 10:36:15

Now that there is support for plugins with pt-table-checksum, I tried to write a plugin to override arguments per table (See Bug #930300 for more details). The arguments that I wanted to override are as follows.

check-plan chunk-size chunk-size-limit columns ignore-columns where

Needless to say, I was unsuccessful. The current implementation of plugins is just not expansive enough to facilitate this ability.

It would be nice if the plugin interface was expanded to allow for overriding arguments per table. One way to do this might be to add the applicable command arguments to the table object and then the tool would use these when checksumming the table. The before_checksum_table hook has access to the table object and so then would be able to change these arguments before the checksum was done.

It also would be nice for a plugin to be able to add arguments to pt-table-checksum. In the above case, I would like to add the argument --arg-table through the plugin interface.