Don't fail is there was some data

When reading the output from spokes-receive-pack, sometimes we get "file
already closed" instead of EOF at the end of the output. In that case,
when there is some data, just log the error and proceed to parsing the
data.

This is an attempt to fix or at least learn more about errors like the
one in https://github.com/github/spokes-receive-pack/actions/runs/4629813916/jobs/8190557968.

internal/integration/hiderefs_test.go

@@ -116,7 +116,7 @@ func TestHiderefsConfig(t *testing.T) {
 		t.Logf("error writing pack to spokes-receive-pack input: %v", err)
 	}
 
-	refStatus, unpackRes, _, err := readResult(bufSRPOut)
+	refStatus, unpackRes, _, err := readResult(t, bufSRPOut)
 	require.NoError(t, err)
 	assert.Equal(t, map[string]string{
 		createBranch:         "ok",

internal/integration/nosideband_test.go

@@ -80,21 +80,25 @@ func TestNoSideBand(t *testing.T) {
 
 	require.NoError(t, srpIn.Close())
 
-	lines, err := readResultNoSideBand(bufSRPOut)
+	lines, err := readResultNoSideBand(t, bufSRPOut)
 	require.NoError(t, err)
 	assert.Equal(t, []string{
 		"unpack ok\n",
 		"ok refs/heads/newbranch\n",
 	}, lines)
 }
 
-func readResultNoSideBand(r io.Reader) ([]string, error) {
+func readResultNoSideBand(t *testing.T, r io.Reader) ([]string, error) {
 	var lines []string
 
 	// Read all of the output so that we can include it with errors.
 	data, err := io.ReadAll(r)
 	if err != nil {
-		return nil, err
+		if len(data) > 0 {
+			t.Logf("got data, but there was an error: %v", err)
+		} else {
+			return nil, err
+		}
 	}
 
 	// Replace r.

internal/integration/parse.go

@@ -51,7 +51,7 @@ func readAdv(r io.Reader) (map[string]string, string, error) {
 	}
 }
 
-func readResult(r io.Reader) (map[string]string, string, [][]byte, error) {
+func readResult(t *testing.T, r io.Reader) (map[string]string, string, [][]byte, error) {
 	var (
 		refStatus map[string]string
 		unpackRes string
@@ -61,7 +61,11 @@ func readResult(r io.Reader) (map[string]string, string, [][]byte, error) {
 	// Read all of the output so that we can include it with errors.
 	data, err := io.ReadAll(r)
 	if err != nil {
-		return nil, "", nil, err
+		if len(data) > 0 {
+			t.Logf("got data, but there was an error: %v", err)
+		} else {
+			return nil, "", nil, err
+		}
 	}
 
 	// Replace r.

internal/integration/pushoptions_test.go

@@ -79,7 +79,7 @@ func TestPushOptions(t *testing.T) {
 
 	require.NoError(t, srpIn.Close())
 
-	refStatus, unpackRes, _, err := readResult(bufSRPOut)
+	refStatus, unpackRes, _, err := readResult(t, bufSRPOut)
 	require.NoError(t, err)
 	assert.Equal(t, map[string]string{
 		createBranch: "ok",