[docs] add push_with_docs script

scripts/publish_docs_branch.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+
+set -Eeuo pipefail
+
+if [[ $# -ne 2 ]]; then
+    echo "usage: $0 <site-dir> <branch>" >&2
+    exit 2
+fi
+
+SITE_DIR="$1"
+BRANCH="$2"
+
+if [[ ! -d "$SITE_DIR" ]]; then
+    echo "site directory not found: $SITE_DIR" >&2
+    exit 1
+fi
+
+if ! git rev-parse --git-dir >/dev/null 2>&1; then
+    echo "must be run inside a git repository" >&2
+    exit 1
+fi
+
+TMP_DIR="$(mktemp -d)"
+cleanup() {
+    git worktree remove --force "$TMP_DIR" >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+git fetch origin "$BRANCH" || true
+
+if git show-ref --verify --quiet "refs/remotes/origin/$BRANCH"; then
+    git worktree add --detach "$TMP_DIR" "origin/$BRANCH"
+else
+    git worktree add --detach "$TMP_DIR"
+    git -C "$TMP_DIR" checkout --orphan "$BRANCH"
+fi
+
+find "$TMP_DIR" -mindepth 1 -maxdepth 1 ! -name '.git' -exec rm -rf {} +
+cp -R "$SITE_DIR"/. "$TMP_DIR"/
+touch "$TMP_DIR/.nojekyll"
+
+git -C "$TMP_DIR" config user.name "${GIT_AUTHOR_NAME:-Forgejo Actions}"
+git -C "$TMP_DIR" config user.email "${GIT_AUTHOR_EMAIL:-forgejo-actions@localhost}"
+git -C "$TMP_DIR" add -A
+
+if git -C "$TMP_DIR" diff --cached --quiet; then
+    echo "no docs changes to publish"
+    exit 0
+fi
+
+git -C "$TMP_DIR" commit -m "Publish docs for ${GITHUB_SHA:-local build}"
+git -C "$TMP_DIR" push --force origin "HEAD:${BRANCH}"