Allow file in --from arg

mount_gpt_image.sh

Index: mount_gpt_image.sh
diff --git a/mount_gpt_image.sh b/mount_gpt_image.sh
index 87324cbbbe617b8bf986162add7b167d8268fb35..dc0491a5d176f35a57d11c876ea40326a60b3f22 100755
--- a/mount_gpt_image.sh
+++ b/mount_gpt_image.sh
@@ -51,7 +51,7 @@ DEFINE_boolean safe $FLAGS_FALSE \
 DEFINE_boolean unmount $FLAGS_FALSE \
   "Unmount previously mounted dir." u
 DEFINE_string from "/dev/sdc" \
-  "Directory containing image or device with image on it" f
+  "Directory, image, or device with image on it" f
 DEFINE_string image "chromiumos_image.bin"\
   "Name of the bin file if a directory is specified in the from flag" i
 DEFINE_string "rootfs_mountpt" "/tmp/m" "Mount point for rootfs" "r"
@@ -68,6 +68,26 @@ eval set -- "${FLAGS_ARGV}"
 # Die on error
 set -e
 
+# Check for conflicting args.
+# If --from is a block device, --image can't also be specified.
+if [ -b "${FLAGS_from}" ]; then
+  if [ "${FLAGS_image}" != "chromiumos_image.bin" ]; then
+    die "-i ${FLAGS_image} can't be used with block device ${FLAGS_from}"
+  fi
+fi
+
+# Allow --from /foo/file.bin
+if [ -f "${FLAGS_from}" ]; then
+  # If --from is specified as a file, --image cannot be also specified.
+  if [ "${FLAGS_image}" != "chromiumos_image.bin" ]; then
+    die "-i ${FLAGS_image} can't be used with --from file ${FLAGS_from}"
+  fi
+  pathname=$(dirname "${FLAGS_from}")
+  filename=$(basename "${FLAGS_from}")
+  FLAGS_image="${filename}"
+  FLAGS_from="${pathname}"
+fi
+
 # Common unmounts for either a device or directory
 function unmount_image() {
   echo "Unmounting image from ${FLAGS_stateful_mountpt}" \