Re: [PATCH] doc: gpg: say which date SSH key lifetimes are checked against

[Junio C Hamano <gitster@pobox.com>]

Christian Noé Ramos López <chris@nortesoftware.dev> writes:

> -Since OpensSSH 8.8 this file allows specifying a key lifetime using valid-after &
> -valid-before options. Git will mark signatures as valid if the signing key was
> -valid at the time of the signature's creation. This allows users to change a
> -signing key without invalidating all previously made signatures.
> +Since OpenSSH 8.8 this file allows specifying a key lifetime using valid-after &
> +valid-before options. When verifying a commit or a tag, Git checks that lifetime
> +against the committer or tagger date recorded in the commit or tag. This allows
> +users to change a signing key without invalidating all previously made
> +signatures. That date is chosen by whoever creates the commit or tag, so it is
> +not evidence of when the signature was made; the same is true of the creation
> +time in a GPG signature, which is set by the signer's clock. Relying on a key
> +lifetime is therefore only safe as long as the signing key has never leaked;
> +once it has, valid-after and valid-before guarantee nothing.

Saying what we compare against may be valuable, but everything else
sounds more like an empty fluff to me.  Isn't it self evident that
validity time range is a useless concept unless you cannot tell when
the signature was made?  In other words, instead of the long
discussion of how useless the validity checks are, something
succinct like

    Since OpensSSH 8.8 this file allows specifying a key lifetime using
    valid-after & valid-before options. Git validates the signature by
    checking the committer or tagger timestamp is within the validity
    time range.  This allows users to change a signing key without
    invalidating all previously made signatures.

should be sufficient, I would have to say.  Or am I missing
something?