lib/config: Format bytes in insufficient space errors (fixes #5920) (#5921)

lib/config/size_test.go

@@ -91,3 +91,42 @@ func TestParseSize(t *testing.T) {
 		}
 	}
 }
+
+func TestFormatSI(t *testing.T) {
+	cases := []struct {
+		bytes  int64
+		result string
+	}{
+		{
+			bytes:  0,
+			result: "0 ", // space for unit
+		},
+		{
+			bytes:  999,
+			result: "999 ",
+		},
+		{
+			bytes:  1000,
+			result: "1.0 K",
+		},
+		{
+			bytes:  1023 * 1000,
+			result: "1.0 M",
+		},
+		{
+			bytes:  5 * 1000 * 1000 * 1000,
+			result: "5.0 G",
+		},
+		{
+			bytes:  50000 * 1000 * 1000 * 1000 * 1000,
+			result: "50000.0 T",
+		},
+	}
+
+	for _, tc := range cases {
+		res := formatSI(tc.bytes)
+		if res != tc.result {
+			t.Errorf("formatSI(%d) => %q, expected %q", tc.bytes, res, tc.result)
+		}
+	}
+}