This is the only place in libextra that Sha1 (or any other hash) is being used. The declare_input() function takes 3 parameters - a kind ("file"), name, and a value which was previously the Sha1 digest of the file. Nothing I can see in the workcache code requires that the 3rd argument be a Sha1 Digest, however. Since this is just a test case and we know that the file is going to be pretty small, what I'm thinking is that we can just use the file contents directly instead of hashing them first. If Sha1 were still in libextra, this would be a bit silly of course. But, it also seems to be a bit overkill to keep Sha1 in libextra just to support this one test case.