Allow re-rendering after config has changed

[jamchamb]

After changing the config we'd want to render our images with new settings, but if the script sees that the source images haven't changed it refuses to re-render. Could check to see if images.yaml is newer than the last outputs.

[rf]

Yeah the way I used to get around this was to just find images/ | xargs touch. touch will just set their last modified date to the current time, so that'll force rebuild. But yeah, that would be a cool feature.

[jamchamb]

I might've jumped the gun on this one. It works, but all output groups will be re-rendered after the config is updated, whereas we really only want to re-render the specific groups that were updated. To do that, we'd have to keep track of the properties used to generate each output file.

It might be possible to use a flat-file to store hashes of each outputConfig by group and do a re-render if we come across an outputConfig that hasn't been seen before (and then prune the ones that no longer exist) in addition to re-rendering when the source images change.

In the meantime, should I undo the changes to ModCheck? I could also just put a --rerender <group(s)> option in its place until something more automatic is implemented.

[jamchamb]

I've been using a simple modification that just puts a hash of the output description into the filename of the build files, and it works pretty well (I think the 9patch plugin has to be updated to work with it, though). The only issue is leftover obsolete build images, but it shouldn't be hard to add a command line option for pruning out configs that no longer exist in images.yaml.