Don't display calculating datastore size on empty repo.

[kevina]

We should detect when a repo was just created (or empty) and avoid displaying this message:

Calculating datastore size. This might take 5m0s at most and will happen only once

[Stebalien]

We can do this with a timeout. That is, fire off a goroutine:

done := make(chan struct{})
cancel := make(chan struct{})

go func() {
    defer close(done)
    select {
    case <-time.After(...):
        fmt.Println(...)
    case <-cancel:
    }
}
// calculate disk usage.
close(cancel)
<-done

This way, we only spam the user when it takes more than, e.g., a second.

[kevina]

We could do that, detecting a new repo is fairly easy though. Just check for the absence of any directories.

[Kubuxu]

It doesn't have to be a "new" repo. If the process takes, for example, less than 5 seconds there is no reason to bother the user.

[Kubuxu]

@kevina can you handle this?

[kevina]

Sorry @Kubuxu I missed your message.

In any case this is now done in #35