Add a way to detect that a source file has not changed since it was last mummified, in which case skip the mummification process for that file.
Things we can probably skip doing are the following:
Reading the resource for metadata (if a metadata files is already present—but what about detecting metadata file changes in the future)?
Reading the resource for processing if the resource has not been modified.
Writing the resource if it already exists and the source was not modified.
We can also add a --full flag that will create a full mummification (analogous to a full vs incremental backup) if present.
Existing behavior will change slightly:
Descriptions will be written after site generation, not before. In fact each description will be written individually, as part of the mummification process.
Every target file will result in a target description, as every description will now contain timestamp and other information necessary for incremental mummification.