Add a patch backport script

plugins/python-build/scripts/backport.sh

@@ -0,0 +1,27 @@
+# source this in Bash
+# cd to git repo of CPython
+
+_python_build_dir=$(cd "${BASH_SOURCE%/*}/.."; pwd -P)
+
+backport() {
+  [[ $# -lt 2 ]] && { echo "usage: $FUNCNAME <commit_hash> <CPython version>..." >&2; return 1; }
+  
+  (set -euxo pipefail
+  sha="${1:?}"
+  shift
+  for b; do
+    git checkout "Branch_v$b" || git checkout -b "Branch_v$b" "v$b"
+    git cherry-pick "$sha"
+    git format-patch -1
+    patch_dir="$_python_build_dir/share/python-build/$b/Python-$b"
+    shopt -s nullglob
+    pp=("$patch_dir"/*.patch)
+    patch_offset=${#pp[@]}
+    shopt -u nullglob
+    unset pp
+    mkdir -p "$patch_dir"
+    for f in *.patch; do
+      mv "$f" "$patch_dir/$(printf '%04d' $((${f::4}+patch_offset)))${f:4}"
+    done
+  done)
+}