Add GitHub Actions workflow to publish packages

.github/workflows/aur/entrypoint.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+
+main() {
+    case "${1:-}" in
+        build)
+            build
+            ;;
+        commit)
+            prepublish
+            git diff origin/master
+            git log --oneline | head -n5
+            ;;
+        publish)
+            prepublish
+            publish
+            ;;
+        shell)
+            exec /bin/bash -
+            ;;
+        *)
+            echo "No such command!" >&2
+            exit 127
+            ;;
+    esac
+}
+
+prepare_pkgbuild() {
+    sed -Ei "s/^pkgver=$/pkgver=${AIOGRAM_VERSION}/" PKGBUILD
+    updpkgsums
+}
+
+build() {
+    prepare_pkgbuild
+    makepkg -sicC --noconfirm --noprogressbar
+}
+
+prepare_git() {
+    mkdir dist && cd dist
+    git init
+    git remote add origin ssh://aur@aur.archlinux.org/python-aiogram.git
+    git pull origin master
+}
+
+commit() {
+    git add PKGBUILD .SRCINFO
+    git commit -m 'New version: v'"${AIOGRAM_VERSION}"
+}
+
+prepublish() {
+    prepare_pkgbuild
+    prepare_git
+    cp ../PKGBUILD ./
+    makepkg --printsrcinfo >.SRCINFO
+    commit
+}
+
+publish() {
+    git push -u origin master
+}
+
+# check whether running as script or sourced by another shell (not reliable)
+if [[ "$(basename $0)" = "entrypoint.sh" ]]; then
+    set -euo pipefail
+    main $@
+fi