Enable receive.fsckObjects in tests

We have this enabled in our prod config, and it changes
spokes-receive-pack in important ways. In particular, it makes
spokes-receive-pack care about bad dates, which we want to disable
sometimes. So let's enable it here (and update the existing tests to
match the new behavior.

Makefile

@@ -90,6 +90,7 @@ go-test-integration:
 
 	# Add our compiled `spokes-receive-pack` to the PATH while running tests:
 	PATH="$(CURDIR)/bin:$(PATH)" \
+	    GIT_CONFIG_SYSTEM="$(CURDIR)/internal/integration/testdata/gitconfig" \
 	    $(GO) test $(TESTINTEGRATIONFLAGS) $(TESTSUITE) 2>&1
 
 	@echo "$(M) disabling failpoints ..."

internal/integration/missingobjects_test.go

@@ -54,9 +54,9 @@ func TestMissingObjects(t *testing.T) {
 	refStatus, unpackRes, _, err := readResult(t, srp.Out)
 	require.NoError(t, err)
 	assert.Equal(t, map[string]string{
-		info.Ref: "ng missing necessary objects",
+		info.Ref: "ng error processing packfiles: exit status 128",
 	}, refStatus)
-	assert.Equal(t, "unpack ok\n", unpackRes)
+	assert.Equal(t, "unpack index-pack failed\n", unpackRes)
 }
 
 func TestDeleteAndUpdate(t *testing.T) {

internal/integration/testdata/gitconfig

@@ -0,0 +1,4 @@
+# This file has a subset of options from our prod /etc/gitconfig.
+
+[receive]
+	fsckObjects = true