Commandline tool to perform operations on tagged collections

 tagcoll takes a collection of items categorized with multiple tags and
 performs various kinds of operations on them:
 .
  * organize the collection in an intuitively navigable hierarchy;
  * discover and show implicit hierarchical relationships between
    tags;
  * apply various transformations to the collection
  * produce a special patch file with the differencies between two collections.
    Such patch files are specific to tagged collections, and can be applied and
    merged more freely than normal diff output;
  * apply a previously generated patch file to a collection.
 .
 tagcoll has been written with the purpose of studying tagged collections and
 experiment with tagged collection algorithms.