Enhance Docker host resolution logic: add candidate endpoints and update environment variable

.forgejo/workflows/publish-container.yml

@@ -71,6 +71,7 @@ jobs:
 
           if [ -n "${DOCKER_HOST:-}" ]; then
             echo "Using configured DOCKER_HOST=${DOCKER_HOST}"
+            echo "DOCKER_HOST=${DOCKER_HOST}" >> "${GITHUB_ENV}"
             exit 0
           fi
 
@@ -80,20 +81,18 @@ jobs:
             exit 0
           fi
 
-          if getent hosts forgejo-docker-in-docker >/dev/null 2>&1; then
-            echo "DOCKER_HOST=tcp://forgejo-docker-in-docker:2375" >> "${GITHUB_ENV}"
-            echo "Resolved DOCKER_HOST from compose service DNS"
-            exit 0
-          fi
+          # Try a set of common candidate endpoints reachable from inside job containers.
+          CANDIDATES="forgejo-docker-in-docker host.docker.internal 172.17.0.1 172.18.0.1 10.0.2.2"
+          for c in $CANDIDATES; do
+            echo "Testing http://${c}:2375/_ping ..."
+            if curl --silent --max-time 2 "http://${c}:2375/_ping" >/dev/null 2>&1 || curl --silent --max-time 2 "http://${c}:2375/version" >/dev/null 2>&1; then
+              echo "DOCKER_HOST=tcp://${c}:2375" >> "${GITHUB_ENV}"
+              echo "Resolved DOCKER_HOST to tcp://${c}:2375"
+              exit 0
+            fi
+          done
 
-          GATEWAY_IP="$(ip route | awk '/default/ { print $3; exit }')"
-          if [ -n "${GATEWAY_IP}" ]; then
-            echo "DOCKER_HOST=tcp://${GATEWAY_IP}:2375" >> "${GITHUB_ENV}"
-            echo "Resolved DOCKER_HOST from container default gateway: ${GATEWAY_IP}"
-            exit 0
-          fi
-
-          echo "Could not determine a reachable Docker daemon endpoint. Set vars.DOCKER_HOST explicitly."
+          echo "Could not determine a reachable Docker daemon endpoint from candidates. Set vars.DOCKER_HOST explicitly."
           exit 1
 
       - name: Check Docker daemon connectivity