support/download/post-process-helpers: add helper function for post process scripts

download post process scripts will often need to unpack the source
code tarball, do some operation, and then repack it. In order to help
with this, post-process-helpers provide an unpack() function and a
repack() function.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

support/download/helpers

@@ -72,5 +72,27 @@ mk_tar_gz() {
     popd >/dev/null
 }
 
+post_process_unpack() {
+    local dest="${1}"
+    local tarball="${2}"
+    local one_file
+
+    mkdir "${dest}"
+    tar -C "${dest}" --strip-components=1 -xf "${tarball}"
+    one_file="$(find "${dest}" -type f -print0 |LC_ALL=C sort -z |head -z -n1 |tr -d "\0")"
+    touch -r "${one_file}" "${dest}.timestamp"
+}
+
+post_process_repack() {
+    local in_dir="${1}"
+    local base_dir="${2}"
+    local out="${3}"
+    local date
+
+    date="@$(stat -c '%Y' "${in_dir}/${base_dir}.timestamp")"
+
+    mk_tar_gz "${in_dir}/${base_dir}" "${base_dir}" "${date}" "${out}"
+}
+
 # Keep this line and the following as last lines in this file.
 # vim: ft=bash