The debug code skips opening (and printing from) the history store if reading from a checkpoint and the session doesn't have a hs_checkpoint set. It will only be set by default when stopped in the middle of an operation on a checkpoint cursor; otherwise (such as the page dumps generated by test_format on failure) it won't be.

We can make wt_debug_cursor_page temporarily substitute in the right checkpoint name when called on a checkpoint cursor. This will make history store entries appear again.

It would be nice to do this in wt_debug_page as well, but there is no reasonable way to get the information. (The correct identity of the matching history store checkpoint is not a property of the tree or the page, only of the global checkpoint, and consequently isn't available.)