Figure out missing pieces

[Jake-Shadle]

Running cargo fetch immediately after cargo fetcher sync still results in several seconds of work on Linux, when it should be basically nothing. There is probably something missing during a sync that cargo relies on for a "freshness" check, but I haven't found a likely culprit. This is far worse on Windows however, which is the bigger problem.

[Jake-Shadle]

I think this was improved a bit with 0.7.0, but there is still a big problem, particularly on Windows with the index. It seems that Windows just reclones the entirety of the index which is very obvious since it takes like 3 minutes, but it's possible the same problem exists on linux, you just don't notice it because the filesystem isn't stupid.