Add a ramdisk-install.d hook path.

We need to be able to do install.d like things for ramdisks
themselves, but install.d runs outside the ramdisk context - and its
likely to break peoples brains if we mangle the two together - so this
adds a new hook point, ramdisk-install, specifically for installing
things into the ramdisk.

Change-Id: I37d1660309cda6e28bd0b316b08f61db4e080613

README.md

@@ -382,6 +382,10 @@ Ramdisk elements support the following files in their element directories:
 * init.d : POSIX shell script fragments that will be appended to the default
   script executed as the ramdisk is booted (/init).
 
+* ramdisk-install.d : called to copy files into the ramdisk. The variable
+  TMP\_MOUNT\_PATH points to the root of the tree that will be packed into
+  the ramdisk.
+
 * udev.d : udev rules files that will be copied into the ramdisk.
 
 ### Element coding standard ###

elements/ramdisk/post-install.d/99-build-ramdisk

@@ -26,15 +26,17 @@ IMAGE_ELEMENT=
 
 mk_build_dir
 mkdir -p $TMP_BUILD_DIR/mnt
-TMP_MOUNT_PATH=$TMP_BUILD_DIR/mnt
+export TMP_HOOKS_PATH=/tmp
+export TMP_MOUNT_PATH=$TMP_BUILD_DIR/mnt
 
-echo "working in $TMP_MOUNT_PATH"
+echo "building ramdisk in $TMP_MOUNT_PATH"
 
 create_ramdisk_base
 populate_lib
 populate_busybox
 populate_init
 populate_udev
+SCRIPT_HOME=/tmp/in_target.d/bin TMP_HOOKS_PATH=/tmp/in_target.d run_d ramdisk-install
 finalise_image
 save_image /tmp/ramdisk
 cp /boot/vmlinuz-${KERNEL_VERSION} /tmp/kernel

lib/common-functions

@@ -192,7 +192,7 @@ function cleanup_dirs () {
     rm -rf $TMP_BUILD_DIR $TMP_IMAGE_DIR
 }
 
-# Run a directory of hooks outside the target.
+# Run a directory of hooks outside the target (that is, no chrooting).
 function run_d() {
     check_element
     check_break before-$1 bash