This continue doesn't actually do much -- there is nothing following this in the loop anyway.

Not sure if this loop is trying to find the first or last valid h.Created from history, if you want the first then don't you want an unconditional break here? If the last you don't need anything and in either case noCreatedTime seems redundant in this loop.

Actually, the loop below looks like a debugged version of this one -- is this just some leftover debug/initial version?

Its supposed to be break

Then is noCreatedTime useful in this variant of the loop, isn't an unconditional break fine?

We want to break after first nil record. Otherwise, the history item for a first metadata command would be the creation time of a base image layer.

So you are looking for the second layer with a timestamp (because the first is always a base layer)? If so I think it'd be worth expanding the comment.

First layer with a timestamp after a record without a timestamp. If there is no such then the last layer with timestamp.

@tonistiigi I think it would be very useful to sum up this conversation in a comment, because I don't think this is obvious at all.

(probably doesn't need saying, but I agree with @tiborvass ...)