image.bbclass, kernel.bbclass: create warning file about deleting deploydir files

New users sometimes delete files in tmp/deploy/images assuming they will
be re-created just by re-running the build, and then are confused when
this doesn't work. To discourage people from doing this, create a file
called README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt in
tmp/deploy/images containing an explanation of what needs to be done to
re-create files there.

Fixes [YOCTO #1315] and [YOCTO #1346].

(From OE-Core rev: 4316c5e9eec67d71f4699102a63a5f968bd8d1d9)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/image.bbclass

@@ -138,6 +138,8 @@ fakeroot do_rootfs () {
 	mkdir -p ${IMAGE_ROOTFS}
 	mkdir -p ${DEPLOY_DIR_IMAGE}
 
+	cp -n ${COREBASE}/meta/files/deploydir_readme.txt ${DEPLOY_DIR_IMAGE}/README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt
+
 	if [ "${USE_DEVFS}" != "1" ]; then
 		for devtable in ${@get_devtable_list(d)}; do
 			makedevs -r ${IMAGE_ROOTFS} -D $devtable

meta/classes/kernel.bbclass

@@ -500,6 +500,8 @@ kernel_do_deploy() {
 	cd ${DEPLOYDIR}
 	rm -f ${KERNEL_IMAGE_SYMLINK_NAME}.bin
 	ln -sf ${KERNEL_IMAGE_BASE_NAME}.bin ${KERNEL_IMAGE_SYMLINK_NAME}.bin
+
+	cp -n ${COREBASE}/meta/files/deploydir_readme.txt ${DEPLOYDIR}/README_-_DO_NOT_DELETE_FILES_IN_THIS_DIRECTORY.txt
 }
 do_deploy[dirs] = "${DEPLOYDIR} ${B}"
 

meta/files/deploydir_readme.txt

@@ -0,0 +1,8 @@
+Files in the deploy directory will not be re-created automatically if you
+delete them. If you do delete a file, you will need to run:
+
+  bitbake -c clean TARGET
+  bitbake TARGET
+
+where TARGET is the name of the appropriate package or target e.g.
+"virtual/kernel" for the kernel, an image, etc.