Allow substitutes for builds that have preferLocalBuild set

Not substituting builds with "preferLocalBuild = true" was a bad idea,
because it didn't take the cost of dependencies into account. For
instance, if we can't substitute a fetchgit call, then we have to
download/build git and all its dependencies.

Partially reverts 5558652709f27e8a887580b77b93c705659d7a4b and adds a
new derivation attribute "allowSubstitutes" to specify whether a
derivation may be substituted.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libstore/misc.hh b/src/libstore/misc.hh
index 144cb7f457cd..d3e31d51f72c 100644
--- a/src/libstore/misc.hh
+++ b/src/libstore/misc.hh
@@ -34,5 +34,7 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
 
 bool willBuildLocally(const Derivation & drv);
 
+bool substitutesAllowed(const Derivation & drv);
+
 
 }