Factored out the code to copy an image and modify it for test

mod_image_for_test.sh

Index: mod_image_for_test.sh
diff --git a/mod_image_for_test.sh b/mod_image_for_test.sh
index 5b93d245c4864e9d4b1ff98f98265a90db7609cb..f848e15488b5cc909b3acb156285fab473c100ef 100755
--- a/mod_image_for_test.sh
+++ b/mod_image_for_test.sh
@@ -51,6 +51,12 @@ DEFINE_boolean yes $FLAGS_FALSE "Answer yes to all prompts" y
 DEFINE_string build_root "/build" \
     "The root location for board sysroots."
 DEFINE_boolean fast ${DEFAULT_FAST} "Call many emerges in parallel"
+DEFINE_boolean inplace $FLAGS_TRUE \
+    "Modify/overwrite the image ${CHROMEOS_IMAGE_NAME} in place.  \
+Otherwise the image will be copied to ${CHROMEOS_TEST_IMAGE_NAME} \
+if needed, and  modified there"
+DEFINE_boolean force_copy ${FLAGS_FALSE} \
+    "Always rebuild test image if --noinplace"
 
 
 # Parse command line
@@ -74,7 +80,7 @@ fi
 # We have a board name but no image set.  Use image at default location
 if [ -z $FLAGS_image ] ; then
   IMAGES_DIR="${DEFAULT_BUILD_ROOT}/images/${FLAGS_board}"
-  FILENAME="chromiumos_image.bin"
+  FILENAME="${CHROMEOS_IMAGE_NAME}"
   FLAGS_image="${IMAGES_DIR}/$(ls -t $IMAGES_DIR 2>&-| head -1)/${FILENAME}"
 fi
 
@@ -172,6 +178,26 @@ install_autotest() {
 
 # main process begins here.
 
+IMAGE_DIR="$(dirname "${FLAGS_image}")"
+
+# Copy the image to a test location if required
+if [ ${FLAGS_inplace} -eq ${FLAGS_FALSE} ]; then
+  TEST_PATHNAME="${IMAGE_DIR}/${CHROMEOS_TEST_IMAGE_NAME}"
+  if [ ! -f "${TEST_PATHNAME}" ] || \
+     [ ${FLAGS_force_copy} -eq ${FLAGS_TRUE} ] ; then
+    echo "Creating test image from original..."
+    ${COMMON_PV_CAT} "${FLAGS_image}" >"${TEST_PATHNAME}" \
+      || die "Cannot copy ${FLAGS_image} to test image"
+    FLAGS_image="${TEST_PATHNAME}"
+  else
+    echo "Using cached test image"
+    exit
+  fi
+
+  # No need to confirm now, since we are not overwriting the main image
+  FLAGS_yes="$FLAGS_TRUE"
+fi
+
 # Make sure this is really what the user wants, before nuking the device
 if [ $FLAGS_yes -ne $FLAGS_TRUE ]; then
   read -p "Modifying image ${FLAGS_image} for test; are you sure (y/N)? " SURE