feat(runner): provide Docker before workflow steps

scripts/gitea-job-started

@@ -10,6 +10,7 @@ while [ "$(date +%s)" -lt "$deadline" ]; do
         -audience ci-job-ready \
         -socketPath "$socket" \
         >/dev/null 2>&1; then
+        /usr/local/libexec/setup-job-docker
         exit 0
     fi
     sleep 1

scripts/setup-job-docker

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if docker info >/dev/null 2>&1; then
+  printf '%s\n' 'job Docker daemon is already ready'
+  exit 0
+fi
+
+storage_size=${DOCKER_DATA_SIZE:-20G}
+storage_driver=${DOCKER_STORAGE_DRIVER:-overlay2}
+wait_seconds=${DOCKER_START_WAIT_SECONDS:-60}
+
+sudo install -d /var/lib/docker
+if ! mountpoint --quiet /var/lib/docker; then
+  printf '%s\n' "preparing ${storage_size} loop-backed Docker storage"
+  if [[ ! -e /dev/loop-control ]]; then
+    sudo mknod /dev/loop-control c 10 237
+  fi
+  for minor in {0..7}; do
+    if [[ ! -e "/dev/loop${minor}" ]]; then
+      sudo mknod "/dev/loop${minor}" b 7 "$minor"
+    fi
+  done
+  sudo truncate -s "$storage_size" /tmp/docker-data.img
+  sudo mkfs.ext4 -F /tmp/docker-data.img
+  loop_device=$(sudo losetup --find --show /tmp/docker-data.img)
+  sudo mount "$loop_device" /var/lib/docker
+else
+  printf '%s\n' 'using mounted Docker storage at /var/lib/docker'
+fi
+
+if [[ -f /sys/fs/cgroup/cgroup.controllers ]]; then
+  sudo sh -c '
+    mkdir -p /sys/fs/cgroup/init
+    while read -r pid; do
+      printf "%s\n" "$pid" \
+        >/sys/fs/cgroup/init/cgroup.procs 2>/dev/null || true
+    done </sys/fs/cgroup/cgroup.procs
+    sed -e "s/ / +/g" -e "s/^/+" \
+      /sys/fs/cgroup/cgroup.controllers \
+      >/sys/fs/cgroup/cgroup.subtree_control
+  '
+fi
+
+sudo nohup dockerd \
+  --host=unix:///var/run/docker.sock \
+  --storage-driver="$storage_driver" \
+  >/tmp/dockerd.log 2>&1 &
+printf '%s\n' 'waiting for job Docker daemon'
+for ((attempt = 0; attempt < wait_seconds; attempt++)); do
+  if docker info >/dev/null 2>&1; then
+    findmnt /var/lib/docker
+    docker info --format \
+      '{{json .ServerVersion}} {{json .Driver}} {{json .CgroupVersion}}'
+    exit 0
+  fi
+  sleep 1
+done
+
+cat /tmp/dockerd.log
+exit 1