Git index cache entries are versioned too strictly

[Jake-Shadle]

Cargo 1.65.0+ no longer uses the HEAD commit id as the cache file revision, but rather the id of the blob where the crate metadata is stored, as seen here. This means that cache entries will always be rejected by the current code if the user has a cargo 1.65.0+. Sorry I didn't notice this when doing #114.

I'm opening this issue so whoever takes over as maintainer (in light of #132) is aware, but I have no intention of fixing it myself since I no longer use this crate.

[Byron]

Thanks for letting us know, and thanks again for your previous contributions!