48/66: programming-2022: Distinguish model and implementation.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository maintenance.

commit 72faaa0483393262ca6a766d9abaf900ef25f33e
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Wed Apr 13 07:52:08 2022 +0200

    programming-2022: Distinguish model and implementation.
    
    * doc/programming-2022/supply-chain.skb (Authenticating Git Checkouts):
    Separate "the model" from the implementation.
---
 doc/programming-2022/supply-chain.skb | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/doc/programming-2022/supply-chain.skb 
b/doc/programming-2022/supply-chain.skb
index 92b99ce..2d2bf73 100644
--- a/doc/programming-2022/supply-chain.skb
+++ b/doc/programming-2022/supply-chain.skb
@@ -616,7 +616,16 @@ authentication mechanism must be able to deal with those 
changes; a
 developer’s signature may only be considered valid for the period during
 which the developer was officially an authorized committer.])
 
-      (p [To implement that, we came up with the following mechanism and rule:
+      (p [The model we devised for ,(emph [checkout authentication]) can
+be described as ,(emph [in-band commit authorization]).  “In-band” means
+that the information necessary to determine whether a commit is
+legitimate—where it was ,(emph [authorized])—is available in the
+repository itself; this check can thus be made off-line, without
+resorting to a third party.  Authorization information follows the
+commit graph: the list of authorized signers for a commit is obtained
+,(emph [in the parent commit(s)]).])
+
+      (p [To implement this model, we came up with the following mechanism and 
rule:
 
 ,(enumerate
     (item [The repository contains a ,(tt [.guix-authorizations])