file CAS URLs support any filename, but not no filename

[abentley]

The filename appears to be irrelevant in file CAS URLs, which is good because at least some error messages contain only hash/size. But the filename should be optional, then, and it's not. A file CAS URL with no filename will produce a 404, with or without a trailing slash.

This requirement goes against the intuitive understanding of a CAS, which is that filenames are irrelevant to it. It's content-addressable, not filename-addressable. Once you know about this quirk, you can supply "asdf" as the filename every time, but it's an unnecessary stumbling block.