- includes aliases
- checks coverage of sequences (assumes full coverage of all unicode
emoji and sequences for now)
- reports sequence names
(Some of this code needs to be shuffled into other places, sequence name
lookup and emoji_vs stripping doesn't belong here since these operations
are more generally useful. That will come.)
- supports checking files with other extension besides .png
- checks all files under a root directory and not just the
files directly in a directory
- checks for duplicate files in multiple directories under a root
- reports the directory containing a file when there are problems