Disable automatic update checks if booting from a removable device.

utils_unittest.cc

Index: utils_unittest.cc
diff --git a/utils_unittest.cc b/utils_unittest.cc
index b67114a9df8472056be784f46c1bf205154c8880..575d91fbb99bee3a244b3c2fe4f3fdd5a6e2e0f3 100644
--- a/utils_unittest.cc
+++ b/utils_unittest.cc
@@ -133,6 +133,23 @@ TEST(UtilsTest, TempFilenameTest) {
 TEST(UtilsTest, RootDeviceTest) {
   EXPECT_EQ("/dev/sda", utils::RootDevice("/dev/sda3"));
   EXPECT_EQ("/dev/mmc0", utils::RootDevice("/dev/mmc0p3"));
+  EXPECT_EQ("", utils::RootDevice("/dev/foo/bar"));
+  EXPECT_EQ("", utils::RootDevice("/"));
+  EXPECT_EQ("", utils::RootDevice(""));
+}
+
+TEST(UtilsTest, SysfsBlockDeviceTest) {
+  EXPECT_EQ("/sys/block/sda", utils::SysfsBlockDevice("/dev/sda"));
+  EXPECT_EQ("", utils::SysfsBlockDevice("/foo/sda"));
+  EXPECT_EQ("", utils::SysfsBlockDevice("/dev/foo/bar"));
+  EXPECT_EQ("", utils::SysfsBlockDevice("/"));
+  EXPECT_EQ("", utils::SysfsBlockDevice("./"));
+  EXPECT_EQ("", utils::SysfsBlockDevice(""));
+}
+
+TEST(UtilsTest, IsRemovableDeviceTest) {
+  EXPECT_FALSE(utils::IsRemovableDevice(""));
+  EXPECT_FALSE(utils::IsRemovableDevice("/dev/non-existent-device"));
 }
 
 TEST(UtilsTest, PartitionNumberTest) {