Thank you for working on this patchset and pushing some of these patches!
I tried to write comments for tts_minimal_is_current_xact_tuple() and tts_minimal_getsomeattrs() for them to be the same as for the same functions for heap and virtual tuple slots, as I proposed above in the thread. (tts_minimal_getsysattr is not introduced by the current patchset, but anyway)
Meanwhile I found that (never appearing) error message for tts_minimal_is_current_xact_tuple needs to be corrected. Please see the patch in the attachment.
I need to correct myself: it's for tts_minimal_getsysattr() not tts_minimal_getsomeattrs()