libutil: return sources from runProgram2

this much more closely mimics what is actually happening: we're reading
data from somewhere else, actively, rather than passively waiting. with
the data flow matching the underlying system interactions better we can
remove a few sinkToSource calls that merely exists to undo the mismatch
caused by not treating subprocess output as a data source to begin with

Change-Id: If4abfc2f8398fb5e88c9b91a8bdefd5504bb2d11

1 files changed, 6 insertions, 9 deletions

diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index 75ac926e2..81c579e84 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -688,17 +688,14 @@ struct GitInputScheme : InputScheme
 
             filter = isNotDotGitDirectory;
         } else {
-            // FIXME: should pipe this, or find some better way to extract a
-            // revision.
-            auto source = sinkToSource([&](Sink & sink) {
-                runProgram2({
-                    .program = "git",
-                    .args = { "-C", repoDir, "--git-dir", gitDir, "archive", input.getRev()->gitRev() },
-                    .standardOut = &sink
-                }).wait();
+            auto proc = runProgram2({
+                .program = "git",
+                .args = { "-C", repoDir, "--git-dir", gitDir, "archive", input.getRev()->gitRev() },
+                .captureStdout = true,
             });
+            Finally const _wait([&] { proc.wait(); });
 
-            unpackTarfile(*source, tmpDir);
+            unpackTarfile(*proc.stdout(), tmpDir);
         }
 
         auto storePath = store->addToStore(name, tmpDir, FileIngestionMethod::Recursive, htSHA256, filter);