libutil: return a source from readFile

don't consume a sink, return a source instead. the only reason to not do
this is a very slight reduction in dynamic allocations, but since we are
going to *at least* do disk io that will not be a lot of overhead anyway

Change-Id: Iae2f879ec64c3c3ac1d5310eeb6a85e696d4614a

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nix/add-to-store.cc b/src/nix/add-to-store.cc
index 39e5cc99d..7dbbbcc56 100644
--- a/src/nix/add-to-store.cc
+++ b/src/nix/add-to-store.cc
@@ -37,7 +37,7 @@ struct CmdAddToStore : MixDryRun, StoreCommand
         Hash hash = narHash;
         if (ingestionMethod == FileIngestionMethod::Flat) {
             HashSink hsink(htSHA256);
-            readFile(path, hsink);
+            readFileSource(path)->drainInto(hsink);
             hash = hsink.finish().first;
         }