Use dib-run-parts for running scripts in target

Also modified dib-run-parts to apply a more workable solution for
filtering out unwanted files such as editor backups and VCS.

The script is installed in its own element, depended on by the OS
specific ubuntu element. This is  because the ubuntu element (and
later other OS's) are responsible for populating the root filesystem.
If we try to install this in base, the root filesystem will look to
be populated already and we will skip automatically choosing ubuntu.

Change-Id: I017646748c1a8360299106289b57d976d45875a8

elements/dib-run-parts/root.d/90-base-dib-run-parts

@@ -0,0 +1,5 @@
+#!/bin/bash
+home=$(dirname $0)
+exec sudo install -m 0755 -o root -g root -D \
+    $home/dib-run-parts \
+    $TARGET_ROOT/usr/local/bin/dib-run-parts

elements/dib-run-parts/root.d/dib-run-parts

@@ -16,6 +16,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+allowed_regex=${RUN_PARTS_REGEX:-"^[0-9A-Za-z_-]+$"}
+
 set -ue
 
 name=$(basename $0)
@@ -41,8 +43,9 @@ if ! [ -d $target_dir ] ; then
 fi
 
 # We specifically only want to sort *by the numbers*.
-# Lexical sorting is not guaranteed.
-targets=$(find $target_dir -type f -executable \! -name '.*' -printf '%f\n' | sort -n)
+# Lexical sorting is not guaranteed, and identical numbers may be
+# parallelized later
+targets=$(find $target_dir -type f -executable -printf '%f\n' | grep -E "$allowed_regex" | LANG=C sort -n)
 
 for target in $targets ; do
     output "Running $target_dir/$target"

elements/ubuntu/element-deps

@@ -1 +1,2 @@
 dpkg
+dib-run-parts

lib/img-functions

@@ -116,7 +116,7 @@ function run_d_in_target() {
       sudo mount --bind ${TMP_HOOKS_PATH} $TMP_MOUNT_PATH/tmp/in_target.d
       sudo mount -o remount,ro,bind ${TMP_HOOKS_PATH} $TMP_MOUNT_PATH/tmp/in_target.d
       check_break before-$1 run_in_target bash
-      run_in_target run-parts /tmp/in_target.d/$1.d
+      run_in_target dib-run-parts /tmp/in_target.d/$1.d
       check_break after-$1 run_in_target bash
       sudo umount -f $TMP_MOUNT_PATH/tmp/in_target.d
       sudo rmdir $TMP_MOUNT_PATH/tmp/in_target.d