[PATCH] Explain how to contribute to reproducible builds in Guix.

[Ludovic Courtès]

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 contribute/guix.md  | 47 +++++++++++++++++++++++++++++++++++++++++++++
 contribute/index.md |  4 ++++
 2 files changed, 51 insertions(+)
 create mode 100644 contribute/guix.md

Hello!

I thought it could be useful to have pointers to help out on reproducible
builds in Guix, so here we go.  Let me know what you think!

Ludo'.

diff --git a/contribute/guix.md b/contribute/guix.md
new file mode 100644
index 0000000..719cd65
--- /dev/null
+++ b/contribute/guix.md
@@ -0,0 +1,47 @@
+---
+layout: default
+title: Contribute to reproducible builds in GNU Guix
+permalink: /contribute/guix/
+---
+
+This page explains how you can contribute to reproducible builds in
+[GNU Guix](https://guix.gnu.org).
+
+## Finding reproducibility issues
+
+You can monitor reproducibility issues by running [`guix
+challenge`](https://guix.gnu.org/manual/en/html_node/Invoking-guix-challenge.html).
+To further investigate, you can specify one or more packages on the
+command line, and ask it to invoke Diffoscope upon failure:
+
+```
+guix challenge git \
+  --diff=diffoscope \
+  --substitute-urls="https://ci.guix.gnu.org https://guix.example.org"
+```
+
+Another option is to rebuild packages locally.  For example, assuming
+you already installed Git on your machine, you can force a rebuild [with
+`--check`](https://guix.gnu.org/manual/en/html_node/Additional-Build-Options.html#build_002dcheck):
+
+```
+guix build git --check --no-grafts --keep-failed
+```
+
+If the new build result differs from the one that was already in store,
+the failed build is kept as `/gnu/store/…-git-1.2.3-check`, allowing you
+to compare it with the original one (without the `-check` suffix).
+
+## Reporting issues
+
+Please report issues by sending email to `bug-guix at gnu.org`.  Each
+message opens a new issues visible in the [bug
+tracker](https://issues.guix.gnu.org).
+
+When investigating, be sure to check [Debian’s reproducibility issue
+inventory](https://tests.reproducible-builds.org/debian/index_issues.html)
+for known problems and solutions.
+
+You can also discuss these issues with other developers on [the Guix
+development mailing list and on the IRC
+channel](https://guix.gnu.org/en/contact).
diff --git a/contribute/index.md b/contribute/index.md
index af63915..e1b8af4 100644
--- a/contribute/index.md
+++ b/contribute/index.md
@@ -42,6 +42,10 @@ Reproducible Builds is distro agnostic, which means we care about all the distri
 
 [Suggestions how to contribute to Reproducible Debian](/contribute/debian/)
 
+## Contribute to reproducible builds in GNU Guix
+
+[Suggestions on how to contribute to reproducible builds in GNU Guix](/contribute/guix)
+
 ## Donate
 
 Another way to help is to financially support our project. We welcome any
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