Same file, different metadata

[remram44]

Currently it is assumed that we will never bump into the same file again, or that if we do, it will be the same file with the exact same set of metadata.

Something should probably be provided to handle the case when we have different metadata.

The possible operations are:

• Joining different sets of metadata (would occur went syncing?). I don't think this is what we want to do.
• Considering the file as different if it has different metadata (i.e. hash metadata+contents)

[remram44]

#23 is more general, closing this.