substitute: Honor client-provided empty URL list.

Befor2021-06-16gnu: Respect ‘rootdelay’ kernel command-line argument....Tobias Geerinckx-Rice
ute.scm (or*): Remove.
(%cache-urls): Use 'or' instead of 'or*'.
* tests/store.scm ("substitute query, alternating URLs"): Add test with
empty URL list.
* doc/guix.texi (Common Build Options): Mention the empty string.

1 files changed, 3 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 05ce7858d5..ba4fe1a826 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -3983,6 +3983,9 @@ This means that substitutes may be downloaded from @var{urls}, provided
 they are signed by a key authorized by the system administrator
 (@pxref{Substitutes}).
 
+When @var{urls} is the empty string, substitutes are effectively
+disabled.
+
 @item --no-substitutes
 Do not use substitutes for build products.  That is, always build things
 locally instead of allowing downloads of pre-built binaries