* Add support to define macros or whatever for Jinja, or to include generic stanzas in any output so adding macros won't mean repeatedly including them.
* It'd be good to generate a dependency tree and only recompile things based on changes, like makefile-like behavior.
* Fragments which would be blobs of mechanics like rss feed, thumbnail links, etc. They would be virtual files and other changes to processing
chains and project contents. `python -mheckweasel --fragment=rss,config=foo.meta` etc.
* Run commands as part of processing chains
* Project level processing chain overrides in the .meta or whatever.
* Project settings in separate file from .meta that would basically do .meta stuff. Like global meta + config in a top.heck file by default and overridable by a parameter.