Add 'guix challenge'.

* guix/scripts/challenge.scm, tests/challenge.scm: New files.
* Makefile.am (MODULES): Add the former.
  (SCM_TESTS): Add the latter.
* doc.am (SUBCOMMANDS): Add 'challenge'.
* doc/guix.texi (Substitutes): Add xref to 'guix challenge'.
  (Invoking guix challenge): New node.
* doc/contributing.texi (Submitting Patches): Add note about using 'guix
  challenge'.
* po/guix/POTFILES.in: Add guix/scripts/challenge.scm.

1 files changed, 11 insertions, 0 deletions

diff --git a/doc/contributing.texi b/doc/contributing.texi
index b2d097dd62..245ce9b1c4 100644
--- a/doc/contributing.texi
+++ b/doc/contributing.texi
@@ -234,6 +234,17 @@ For important changes, check that dependent package (if applicable) are
 not affected by the change; @code{guix refresh --list-dependent
 @var{package}} will help you do that (@pxref{Invoking guix refresh}).
 
+@item
+Check whether the package's build process is deterministic.  This
+typically means checking whether an independent build of the package
+yields the exact same result that you obtained, bit for bit.
+
+A simple way to do that is with @command{guix challenge}
+(@pxref{Invoking guix challenge}).  You may run it once the package has
+been committed and built by @code{hydra.gnu.org} to check whether it
+obtains the same result as you did.  Better yet: Find another machine
+that can build it and run @command{guix publish}.
+
 @end enumerate
 
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