contrib: add "git-subtree-reimport.sh" script

contrib/scripts/git-subtree-reimport.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -ex
+
+cd "$(dirname "$(readlink -f "$0")")/../.."
+
+reimport() {
+    local d="$1"
+    local project
+    local branch
+
+    if [[ "$d" = c-* ]] ; then
+        project=c-util
+        branch=main
+    else
+        project=nettools
+        branch=master
+    fi
+
+    git subtree pull --prefix "src/$d" "git@github.com:$project/$d.git" "$branch" --squash -m \
+"$d: re-import git-subtree for 'src/$d'
+
+  git subtree pull --prefix src/$d git@github.com:$project/$d.git $branch --squash
+"
+}
+
+reimport_all() {
+    for d in c-list c-rbtree c-siphash c-stdaux n-acd n-dhcp4 ; do
+        reimport "$d"
+    done
+}
+
+reimport_all