fold_patch_ids
fold_patch_ids(
patch_ids: collections.abc.Sequence[str] ,
)-> ‘str’
Return the patch id of a patch combined from several.
Ordered, and not deduplicated: how many patches went in and in what order is part of what the data is, so stacking a patch with itself is not the same datum as the patch alone.
A single id folds to itself, so an operation which combines one patch with nothing leaves the id where it was.