nix-channel: Use binary caches advertised by channels

Channels can now advertise a binary cache by creating a file
<channel-url>/binary-cache-url.  The channel unpacker puts these in
its "binary-caches" subdirectory.  Thus, the URLS of the binary caches
for the channels added by root appear in
/nix/var/nix/profiles/per-user/eelco/channels/binary-caches/*.  The
binary cache substituter reads these and adds them to the list of
binary caches.

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/manual/conf-file.xml b/doc/manual/conf-file.xml
index c09d46206a23..ae167fb787c7 100644
--- a/doc/manual/conf-file.xml
+++ b/doc/manual/conf-file.xml
@@ -329,6 +329,18 @@ build-use-chroot = /dev /proc /bin</programlisting>
   </varlistentry>
 
 
+  <varlistentry><term><literal>binary-caches-files</literal></term>
+
+    <listitem><para>A list of names of files that will be read to
+    obtain additional binary cache URLs.  The default is
+    <literal>/nix/var/nix/profiles/per-user/root/channels/binary-caches/*</literal>,
+    which ensures that Nix will use the binary caches corresponding to
+    the channels installed by root.  Do not set this option to read
+    files created by untrusted users!</para></listitem>
+
+  </varlistentry>
+
+
   <varlistentry><term><literal>trusted-binary-caches</literal></term>
 
     <listitem><para>A list of URLs of binary caches, separated by