Document IndexEntry.path a bit

[pkgw]

I've just started trying to use this library and had some questions about the semantics of the IndexEntry.path field. I've added a brief docstring to record my findings for posterity.

[ehuss]

There's some more detail in git's documentation: https://github.com/git/git/blob/a08a83db2bf27f015bec9a435f6d73e223c21c5e/Documentation/technical/index-format.txt#L107-L124

Interestingly, it looks like libgit2 decompresses the version 4 paths automatically.

[alexcrichton]

@pkgw want to add a reference and/or extra bits from the docs @ehuss linked?

[pkgw]

@alexcrichton Done, plus mentioning the existence of util::bytes2path if one wants to see how to turn these bytes into a path.

[alexcrichton]

👍