cmd/go: set GIT_TRACE_CURL for tests on builders

We have noticed a pattern of connection timeouts connecting to
github.com on the builders. Adding tracing may shed some light on the
underlying cause.

For #52545.

Change-Id: Ic73b494be9a3ea8ce3c7631ee8f62bd3d0d8e7bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/409575
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/go/go_test.go

@@ -287,6 +287,14 @@ func TestMain(m *testing.M) {
 		os.Setenv("GOCACHE", testGOCACHE) // because $HOME is gone
 	}
 
+	if testenv.Builder() != "" || os.Getenv("GIT_TRACE_CURL") == "1" {
+		// To help diagnose https://go.dev/issue/52545,
+		// enable tracing for Git HTTPS requests.
+		os.Setenv("GIT_TRACE_CURL", "1")
+		os.Setenv("GIT_TRACE_CURL_NO_DATA", "1")
+		os.Setenv("GIT_REDACT_COOKIES", "o,SSO,GSSO_Uberproxy")
+	}
+
 	r := m.Run()
 	if !*testWork {
 		removeAll(testTmpDir) // os.Exit won't run defer

src/cmd/go/script_test.go

@@ -190,6 +190,14 @@ func (ts *testScript) setup() {
 		"/=" + string(os.PathSeparator),
 		"CMDGO_TEST_RUN_MAIN=true",
 	}
+	if testenv.Builder() != "" || os.Getenv("GIT_TRACE_CURL") == "1" {
+		// To help diagnose https://go.dev/issue/52545,
+		// enable tracing for Git HTTPS requests.
+		ts.env = append(ts.env,
+			"GIT_TRACE_CURL=1",
+			"GIT_TRACE_CURL_NO_DATA=1",
+			"GIT_REDACT_COOKIES=o,SSO,GSSO_Uberproxy")
+	}
 	if !testenv.HasExternalNetwork() {
 		ts.env = append(ts.env, "TESTGONETWORK=panic", "TESTGOVCS=panic")
 	}