fix: give each Dockerfile action image its own ID (#1372)

Identical Dockerfile builds in concurrent jobs share one image ID under their per-job tags. When a job ends and removes its tag, the daemon deletes the image while another job's build is about to tag it, failing that job with `No such image`. This also hits `TestRunEvent` in CI, where two parallel subtests build the same action.

Label each build with its tag, so every job gets its own image on top of the shared cached layers and removing it never touches another job's.

Reviewed-on: https://gitea.com/gitea/runner/pulls/1372
Reviewed-by: bircni <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>

act/container/docker_build.go

@@ -48,6 +48,7 @@ func NewDockerBuildExecutor(input NewDockerBuildExecutorInput) common.Executor {
 
 		options := client.ImageBuildOptions{
 			Tags:        []string{input.ImageTag},
+			Labels:      map[string]string{"com.gitea.runner.image": input.ImageTag}, // own image ID per tag, so removing one never deletes another job's identical build
 			Remove:      true,
 			AuthConfigs: LoadDockerAuthConfigs(ctx),
 			Dockerfile:  input.Dockerfile,

act/container/docker_build_test.go

@@ -18,10 +18,12 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestDockerBuildReportsDaemonError(t *testing.T) {
+func TestDockerBuildLabelsImageWithItsTagAndReportsDaemonError(t *testing.T) {
+	var labels string
 	daemon := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
 		writer.Header().Set("API-Version", "1.47")
 		if strings.HasSuffix(request.URL.Path, "/build") {
+			labels = request.URL.Query().Get("labels")
 			writer.Header().Set("Content-Type", "application/json")
 			writer.WriteHeader(http.StatusInternalServerError)
 			_, _ = io.WriteString(writer, `{"message":"build rejected"}`)
@@ -35,6 +37,7 @@ func TestDockerBuildReportsDaemonError(t *testing.T) {
 	require.ErrorContains(t, NewDockerBuildExecutor(NewDockerBuildExecutorInput{
 		ImageTag: "action:test", Dockerfile: "Dockerfile", BuildContext: strings.NewReader(""),
 	})(t.Context()), "build rejected")
+	require.JSONEq(t, `{"com.gitea.runner.image":"action:test"}`, labels)
 }
 
 func TestCreateBuildContextFollowsDockerignoreAndSymlinkedRootButKeepsDockerfile(t *testing.T) {