Fix duration saying never when it's unlimited

internal/config/config_test.go

@@ -78,6 +78,14 @@ func TestFormatRoundTrips(t *testing.T) {
 		if got, err := ParseDuration(FormatDuration(d)); err != nil || got != d {
 			t.Errorf("FormatDuration(%s) = %q, which parses back to %s (%v)", d, FormatDuration(d), got, err)
 		}
+		// FormatLifetime reaches the upload form as the expiry placeholder, so
+		// what it prints has to be something a caller could type back.
+		if got, err := ParseDuration(FormatLifetime(d)); err != nil || got != d {
+			t.Errorf("FormatLifetime(%s) = %q, which parses back to %s (%v)", d, FormatLifetime(d), got, err)
+		}
+	}
+	if got := FormatLifetime(Unlimited); got != "unlimited" {
+		t.Errorf("FormatLifetime(Unlimited) = %q, want %q", got, "unlimited")
 	}
 }
 

internal/config/parse.go

@@ -103,6 +103,16 @@ func ParseDuration(s string) (time.Duration, error) {
 	return d, nil
 }
 
+// FormatLifetime renders a lifetime *limit*, where FormatDuration's "never"
+// would describe the wrong thing: a ceiling of Unlimited is not a file that
+// never expires, it is the absence of a ceiling.
+func FormatLifetime(d time.Duration) string {
+	if d == Unlimited {
+		return "unlimited"
+	}
+	return FormatDuration(d)
+}
+
 // FormatDuration is the human-facing inverse of ParseDuration.
 func FormatDuration(d time.Duration) string {
 	switch {