What's the purpose of the meta file?

This is really great work! I've started a port in go to get a better understanding of the code base.

What's the purpose of the separate `meta` file? It appears that it's only opened and closed to read/write a key on start-up. However (if I'm reading the code correctly) any new meta information on `commit` is written to the actual log file. I don't see where the `meta` file itself is updated on subsequent commits. Is the purpose of the meta file simply to hold the key? Thanks!

Start by tracing how the separate `meta` file is opened and closed during startup, then compare that path with the metadata written during `commit`. Confirm whether the file is intended only to hold the key; done means explaining its purpose and documenting how it relates to the log file.

Written by the indexing model from the issue text.