starts_with for Bytes type

[dcz-self]

I'm storing hashes in the database as the Bytes type. The hashes are long enough that I don't always need to query the entire hash (see how git show $HASH does not need the entire hash, but just the beginning). Would it make sense to extend starts_with to Bytes? I'm ready to implement it.

[dcz-self]

Alternatively, a way to extract a slice from the bytes would also be helpful.

[zh217]

Good idea, I will do it now.