01/01: website: reproducible-build-summit-2019: More cool hacks.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix-artwork.

commit 9a525847802972a03dc23a9633048eb36967b93a
Author: Ludovic Courtès <address@hidden>
Date:   Mon Dec 9 11:53:09 2019 +0100

    website: reproducible-build-summit-2019: More cool hacks.
    
    * website/drafts/reproducible-build-summit-2019.md (More cool hacks): 
Expound.
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diff --git a/website/drafts/reproducible-build-summit-2019.md 
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@@ -35,14 +35,34 @@ life on the roof top of the lovely riad that was home to 
the summit.
 # More cool hacks
 
   - Ten Years reproducibility challenge
-  - [system provenance
-    tracking](https://issues.guix.gnu.org/issue/38441)
-  - [guix challenge --diff](https://issues.guix.gnu.org/issue/38518)
+
+During the summit, support for [_system provenance tracking_ in `guix
+system`](https://issues.guix.gnu.org/issue/38441) landed in Guix.  This
+allows a deployed system to embed the information needed to rebuild it:
+its
+[channels](https://guix.gnu.org/manual/devel/en/html_node/Channels.html)
+and its [configuration
+file](https://guix.gnu.org/manual/devel/en/html_node/Using-the-Configuration-System.html).
+In other words, the result is what we could call a _source-carrying
+system_, which could also be thought of as [a sort of
+Quine](https://en.wikipedia.org/wiki/Quine_(computing)).  For users it’s
+a convenient way to map a running system or virtual machine image back
+to its source, or to verify that its binaries are genuine by rebuiling
+it.
+
+The [`guix
+challenge`](https://guix.gnu.org/manual/devel/en/html_node/Invoking-guix-challenge.html)
+command started its life [shortly before first
+summit](https://guix.gnu.org/blog/2015/reproducible-builds-a-means-to-an-end/).
+During this year’s hacking sessions, it [gained a `--diff`
+option](https://issues.guix.gnu.org/issue/38518) that automates the
+steps of downloading, decompressing, and diffing non-reproducible
+archives, possibly with [Diffoscope](https://diffoscope.org/).
 
 # Thanks!
 
 We are grateful to everyone who made this summit possible: Gunner and
-Evelyn of Aspiration, Hannes, Holger, Lamby, and Mattia, as well as our
+Evelyn of Aspiration, Hannes, Holger, Lamby, Mattia, and Vagrant, as well as 
our
 kind hosts at Priscilla.  And of course, thanks to all fellow
 participants whose openmindedness and focus made this both a productive
 and a pleasant experience!