ci: add script to run libbpf sync non-interactively

Run sync-kernel.sh with stdin from /dev/null, so that any prompt asking
for human input fails the sync.

The exit code of sync-kernel.sh isn't reliable (e.g., it exits with 0
when interrupted), so tell from its output whether the sync went
through or there was nothing to sync.

On success, leave a bundle with the sync branch, patches and a pull
request description with the sync log in the output directory.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>

.github/scripts/sync-run.sh

@@ -0,0 +1,107 @@
+#!/bin/bash
+#
+# Run scripts/sync-kernel.sh non-interactively: with stdin at EOF, any prompt
+# asking for human input fails the sync. If the sync went through, <out-dir>
+# gets everything needed to publish it: a bundle with the sync branch,
+# patches, and a pull request description including the sync log.
+#
+# Exits with 0 if the sync went through or there was nothing to sync.
+
+usage () {
+	echo "USAGE: $0 <libbpf-repo> <linux-repo> <out-dir>"
+	echo ""
+	echo "<linux-repo> is expected to be set up by sync-fetch-kernel.sh."
+	exit 1
+}
+
+set -euo pipefail
+
+if [ $# -ne 3 ]; then
+	usage
+fi
+
+LIBBPF_REPO=$(realpath "$1")
+LINUX_REPO=$(realpath "$2")
+OUT_DIR=$(realpath -m "$3")
+GITHUB_OUTPUT=${GITHUB_OUTPUT:-/dev/null}
+GITHUB_STEP_SUMMARY=${GITHUB_STEP_SUMMARY:-/dev/null}
+# Pull request descriptions are limited to 65536 characters
+PR_LOG_MAX=60000
+
+cd "${LIBBPF_REPO}"
+base_sha=$(git rev-parse HEAD)
+old_next=$(cat CHECKPOINT-COMMIT)
+old_bpf=$(cat BPF-CHECKPOINT-COMMIT)
+
+mkdir -p "${OUT_DIR}/tmp"
+# Keep sync-kernel.sh's temporary files around for post-mortem
+export TMPDIR="${OUT_DIR}/tmp"
+log="${OUT_DIR}/sync.log"
+
+# The exit code of sync-kernel.sh can't be trusted (e.g., it exits with 0 when
+# interrupted), so tell from its output how it went
+"${LIBBPF_REPO}/scripts/sync-kernel.sh" "${LIBBPF_REPO}" "${LINUX_REPO}" bpf-master \
+	< /dev/null 2>&1 | tee "${log}" || true
+# Drop progress output overwritten with carriage returns
+sed -i 's/^.*\r//' "${log}"
+
+if grep -qF 'No new changes to apply, we are done!' "${log}"; then
+	echo "::notice::No new libbpf changes since bpf-next ${old_next:0:12} and bpf ${old_bpf:0:12}"
+	exit 0
+fi
+if ! grep -qF 'Great! Content is identical!' "${log}"; then
+	echo "::error::Sync needs a human, see SYNC.md. The sync log and leftovers are in the run's artifact."
+	exit 1
+fi
+
+branch=$(git symbolic-ref --short HEAD)
+git format-patch -q -o "${OUT_DIR}/patches" "${base_sha}..HEAD"
+git bundle create -q "${OUT_DIR}/sync.bundle" "${base_sha}..refs/heads/${branch}"
+
+if [ -n "${GITHUB_RUN_ID:-}" ]; then
+	origin="[workflow run](${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID})"
+else
+	origin="a local run"
+fi
+new_files=$(git diff --name-only --diff-filter=A "${base_sha}" HEAD -- src include)
+
+{
+	echo "Automated libbpf sync from bpf-next and bpf trees, created by ${origin}."
+	echo ""
+	echo "| Tree | Baseline | Checkpoint |"
+	echo "| --- | --- | --- |"
+	echo "| bpf-next | ${old_next} | $(cat CHECKPOINT-COMMIT) |"
+	echo "| bpf | ${old_bpf} | $(cat BPF-CHECKPOINT-COMMIT) |"
+	echo ""
+	echo "CI runs for this pull request have to be approved by a maintainer. If CI needs" \
+	     "adjustments (allow/deny lists, \`ci/diffs\`, \`src/Makefile\`, see SYNC.md), push them to" \
+	     "this branch."
+	if [ -n "${new_files}" ]; then
+		echo ""
+		echo "New files were synced, check if \`src/Makefile\` needs updating:"
+		echo ""
+		# shellcheck disable=SC2016
+		sed 's/^/- `/; s/$/`/' <<< "${new_files}"
+	fi
+	echo ""
+	echo "<details>"
+	echo "<summary>sync-kernel.sh output</summary>"
+	echo ""
+	echo '````'
+	head -c "${PR_LOG_MAX}" "${log}"
+	if (($(wc -c < "${log}") > PR_LOG_MAX)); then
+		echo ""
+		echo "[... truncated, the full log is in the workflow run's artifact ...]"
+	fi
+	echo '````'
+	echo ""
+	echo "</details>"
+} > "${OUT_DIR}/pr-body.md"
+
+cat "${OUT_DIR}/pr-body.md" >> "${GITHUB_STEP_SUMMARY}"
+{
+	echo "branch=${branch}"
+	echo "head_sha=$(git rev-parse HEAD)"
+} >> "${GITHUB_OUTPUT}"
+
+echo "Synced $(git rev-list --count "${base_sha}..HEAD") commits into ${branch}"