Function encode 

pub fn encode(bytes: impl AsRef<[u8]>) -> String

Encode bytes as lowercase hex, two characters per byte.

Byte-for-byte identical to what format!("{:x}", digest) produced under sha2 0.10, which matters: existing blob filenames, catalog index entries, and recorded graph fingerprints were all written with the old formatting, and a change here would silently invalidate every one of them.