Add option to verify build determinism

Passing "--option build-repeat <N>" will cause every build to be
repeated N times. If the build output differs between any round, the
build is rejected, and the output paths are not registered as
valid. This is primarily useful to verify build determinism. (We
already had a --check option to repeat a previously succeeded
build. However, with --check, non-deterministic builds are registered
in the DB. Preventing that is useful for Hydra to ensure that
non-deterministic builds don't end up getting published at all.)

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/manual/command-ref/conf-file.xml b/doc/manual/command-ref/conf-file.xml
index c947d19fa0..71a3495090 100644
--- a/doc/manual/command-ref/conf-file.xml
+++ b/doc/manual/command-ref/conf-file.xml
@@ -616,6 +616,18 @@ flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
   </varlistentry>
 
 
+  <varlistentry xml:id="conf-build-repeat"><term><literal>build-repeat</literal></term>
+
+    <listitem><para>How many times to repeat builds to check whether
+    they are deterministic. The default value is 0. If the value is
+    non-zero, every build is repeated the specified number of
+    times. If the contents of any of the runs differs from the
+    previous ones, the build is rejected and the resulting store paths
+    are not registered as “valid” in Nix’s database.</para></listitem>
+
+  </varlistentry>
+
+
 </variablelist>
 
 </para>