Makefile: Add canary for tests using outside Git envvars

In order to catch cases early where we do not sanitize Git environment
variables passed to us by the outside, this commit adds a canary to our
Makefile by setting `GIT_DIR=/dev/null` for our tests. If any test does
not sanitize envvars, then our spawned Git commands would pick up this
envvar, assume it as their repository path and (hopefully) end up
failing in a controlled way.

This does indeed detect one case where we spawn Git commands but don't
yet sanitize the environment, which is also getting fixed by this
commit.

2 files changed, 20 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index ac5731c15..806d646e3 100644
--- a/Makefile
+++ b/Makefile
@@ -165,6 +165,7 @@ find_go_sources       = $(shell find ${SOURCE_DIR} -type d \( -name ruby -o -nam
 # TEST_OPTIONS: any additional options
 # TEST_PACKAGES: packages which shall be tested
 run_go_tests = PATH='${SOURCE_DIR}/internal/testhelper/testdata/home/bin:${PATH}' \
+    GIT_DIR=/dev/null \
     go test -tags '${GO_BUILD_TAGS}' ${TEST_OPTIONS} ${TEST_PACKAGES}
 
 unexport GOROOT
diff --git a/internal/gitaly/config/testhelper_test.go b/internal/gitaly/config/testhelper_test.go
new file mode 100644
index 000000000..04e13330d
--- /dev/null
+++ b/internal/gitaly/config/testhelper_test.go
@@ -0,0 +1,19 @@
+package config_test
+
+import (
+	"os"
+	"testing"
+
+	"gitlab.com/gitlab-org/gitaly/internal/testhelper"
+)
+
+func TestMain(m *testing.M) {
+	os.Exit(testMain(m))
+}
+
+func testMain(m *testing.M) int {
+	defer testhelper.MustHaveNoChildProcess()
+	cleanup := testhelper.Configure()
+	defer cleanup()
+	return m.Run()
+}