Allow resetting of tag_lists and cached_tag_lists

[bradly]

We have a tag admin area and when a tag was renamed we didn't have an easy way to update the associated cached tag lists of objects with that tag. This patch doesn't add the functionality directly, but it does give a helper method so you can loop through object.tagged_with(some_tag) and then refresh the object's cached tag list. I'm open to add more of this into the gem too, but wanted to start small and see if there is interest first.

Also, this is my first patch for this project so any feedback you have on code organization, format, or anything else, just let me know. Thanks!

[seuros]

I think that renaming tags is bad. It will take too long for large database to invalidate the cache.

cc @bf4

[bradly]

@seuros Interesting. Every app that I've worked on with tags has needed an admin area for someone to normalize tags (for instance when you have a tag 'w2' and a tag 'w-2'). Also, this isn't only for renaming tags; when a tag is deleted you need to updated the cached tags lists as well.

[seuros]

@bradly , that make sense.

@bf4 , what do you think about this ?

[bf4]

Sorry @seuros totally caught up in other things... But I did just release a 3.1.0.rc1 https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md#310rc1--2014-02-26

[joker-777]

Hi, I also was looking for a way to refresh the cached_tag_list field. I kind of assumed that the before_save hook would actually get a fresh list. I was surprised when I realized that it uses tag_list_cache_on which returns the cached version (after checking for an existing instance variable which makes sense). Changing this behavior would make your helper method unnecessary, right?