feat: offline mode for new action cache (#2173)

* Try fetch update of the action, otherwise use cached version

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

cmd/root.go

@@ -562,8 +562,16 @@ func newRunCommand(ctx context.Context, input *Input) func(*cobra.Command, []str
 			ContainerNetworkMode:               docker_container.NetworkMode(input.networkName),
 		}
 		if input.useNewActionCache {
-			config.ActionCache = &runner.GoGitActionCache{
-				Path: config.ActionCacheDir,
+			if input.actionOfflineMode {
+				config.ActionCache = &runner.GoGitActionCacheOfflineMode{
+					Parent: runner.GoGitActionCache{
+						Path: config.ActionCacheDir,
+					},
+				}
+			} else {
+				config.ActionCache = &runner.GoGitActionCache{
+					Path: config.ActionCacheDir,
+				}
 			}
 		}
 		r, err := runner.New(config)

pkg/runner/action_cache_offline_mode.go

@@ -0,0 +1,41 @@
+package runner
+
+import (
+	"context"
+	"io"
+	"path"
+
+	git "github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+)
+
+type GoGitActionCacheOfflineMode struct {
+	Parent GoGitActionCache
+}
+
+func (c GoGitActionCacheOfflineMode) Fetch(ctx context.Context, cacheDir, url, ref, token string) (string, error) {
+	sha, fetchErr := c.Parent.Fetch(ctx, cacheDir, url, ref, token)
+	gitPath := path.Join(c.Parent.Path, safeFilename(cacheDir)+".git")
+	gogitrepo, err := git.PlainOpen(gitPath)
+	if err != nil {
+		return "", fetchErr
+	}
+	refName := plumbing.ReferenceName("refs/action-cache-offline/" + ref)
+	r, err := gogitrepo.Reference(refName, true)
+	if fetchErr == nil {
+		if err != nil || sha != r.Hash().String() {
+			if err == nil {
+				refName = r.Name()
+			}
+			ref := plumbing.NewHashReference(refName, plumbing.NewHash(sha))
+			_ = gogitrepo.Storer.SetReference(ref)
+		}
+	} else if err == nil {
+		return r.Hash().String(), nil
+	}
+	return sha, fetchErr
+}
+
+func (c GoGitActionCacheOfflineMode) GetTarArchive(ctx context.Context, cacheDir, sha, includePrefix string) (io.ReadCloser, error) {
+	return c.Parent.GetTarArchive(ctx, cacheDir, sha, includePrefix)
+}