[cli] Add tooling for cli

cli/cli.go

@@ -0,0 +1,11 @@
+package cli
+
+import "os"
+
+func SetDefaultValueFromEnv(value *string, key string, defaultValue string) {
+	if os.Getenv(key) != "" {
+		*value = os.Getenv(key)
+	} else {
+		*value = defaultValue
+	}
+}

cli/cli_test.go

@@ -0,0 +1,30 @@
+package cli
+
+import (
+	"os"
+	"testing"
+)
+
+func TestSetDefaultValueFromEnv(t *testing.T) {
+	err := os.Setenv("KEY1", "value1")
+	if err != nil {
+		t.Errorf("unable to set env value: %v", err)
+	}
+
+	cases := []struct{
+		key string
+		defValue string
+		expected string
+	}{
+		{"MISSING_KEY", "default", "default"},
+		{"KEY1", "bad value", "value1"},
+	}
+
+	for _, c := range cases {
+		var value = ""
+		SetDefaultValueFromEnv(&value, c.key, c.defValue)
+		if c.expected != value {
+			t.Errorf("SetDefaultValueFromEnv(*value, %v, %v): %v, wants %v", c.key, c.defValue, value, c.expected)
+		}
+	}
+}