Pre-hash passwords to avoid max character limit in bcrypt

[Kaptard]

The issue is that technically, bcrypt can only handle 72 bytes of data, minus one byte for the null terminator.

One way to avoid this is by pre-hashing passwords with something like sha256 or sha512. This should always give us a fixed byte length. However, this leads to the issue that the sha hash effectively becomes the password, meaning one would lose the maximum possible entropy when using high-entropy passwords. On the other hand, it may actually increase the entropy of most common passwords, as long as they're not part of rainbowtables.

I'm not quite sure how to go about this, so any feedback would be appreciated.