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/hash.cc b/src/nix/hash.cc
index 9feca9345..66c5516e7 100644
--- a/src/nix/hash.cc
+++ b/src/nix/hash.cc
@@ -85,7 +85,7 @@ struct CmdHashBase : Command
 
             switch (mode) {
             case FileIngestionMethod::Flat:
-                readFile(path, *hashSink);
+                readFileSource(path)->drainInto(*hashSink);
                 break;
             case FileIngestionMethod::Recursive:
                 dumpPath(path, *hashSink);