Is there a way to use an old cache but force an update to the cache when saving?

[Imberflur]

The main way I know to force an update to the cache is changing the prefix-key, but AFAIK that will start from scratch instead of reusing an old cache entry.

I'm trying to debug why some dependencies are being rebuilt and it would be a quicker debug process if I could reuse the current cache when updating the cache (ofc if I'm able to identify the issue, I would want to do a final test from a clean slate to make sure things aren't just working due to the cache built up during debugging).

[Imberflur]

Looking at the source for how the restore key vs the full cache key are computed, it seems like I may be able to edit a comment in .cargo/config.toml as a workaround for this.