Implements no-op before CheckoutTag in gogit

Signed-off-by: Somtochi Onyekwere <somtochionyekwere@gmail.com>

pkg/git/gogit/checkout.go

@@ -29,6 +29,7 @@ import (
 	"github.com/go-git/go-git/v5/config"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/go-git/go-git/v5/plumbing/transport"
 	"github.com/go-git/go-git/v5/storage/memory"
 
 	"github.com/fluxcd/pkg/gitutil"
@@ -46,7 +47,7 @@ func CheckoutStrategyForOptions(_ context.Context, opts git.CheckoutOptions) git
 	case opts.SemVer != "":
 		return &CheckoutSemVer{SemVer: opts.SemVer, RecurseSubmodules: opts.RecurseSubmodules}
 	case opts.Tag != "":
-		return &CheckoutTag{Tag: opts.Tag, RecurseSubmodules: opts.RecurseSubmodules}
+		return &CheckoutTag{Tag: opts.Tag, RecurseSubmodules: opts.RecurseSubmodules, LastRevision: opts.LastRevision}
 	default:
 		branch := opts.Branch
 		if branch == "" {
@@ -71,19 +72,11 @@ func (c *CheckoutBranch) Checkout(ctx context.Context, path, url string, opts *g
 	ref := plumbing.NewBranchReferenceName(c.Branch)
 	// check if previous revision has changed before attempting to clone
 	if c.LastRevision != "" {
-		config := &config.RemoteConfig{
-			Name: git.DefaultOrigin,
-			URLs: []string{url},
-		}
-		rem := extgogit.NewRemote(memory.NewStorage(), config)
-		refs, err := rem.List(&extgogit.ListOptions{
-			Auth: authMethod,
-		})
+		currentRevision, err := getLastRevision(url, ref, opts, authMethod)
 		if err != nil {
-			return nil, fmt.Errorf("unable to list remote for '%s': %w", url, err)
+			return nil, err
 		}
 
-		currentRevision := filterRefs(refs, ref)
 		if currentRevision != "" && currentRevision == c.LastRevision {
 			return nil, git.NoChangesError{
 				Message:          "no changes since last reconcilation",
@@ -119,9 +112,31 @@ func (c *CheckoutBranch) Checkout(ctx context.Context, path, url string, opts *g
 	return buildCommitWithRef(cc, ref)
 }
 
+func getLastRevision(url string, ref plumbing.ReferenceName, opts *git.AuthOptions, authMethod transport.AuthMethod) (string, error) {
+	config := &config.RemoteConfig{
+		Name: git.DefaultOrigin,
+		URLs: []string{url},
+	}
+	rem := extgogit.NewRemote(memory.NewStorage(), config)
+	listOpts := &extgogit.ListOptions{
+		Auth: authMethod,
+	}
+	if opts != nil && opts.CAFile != nil {
+		listOpts.CABundle = opts.CAFile
+	}
+	refs, err := rem.List(listOpts)
+	if err != nil {
+		return "", fmt.Errorf("unable to list remote for '%s': %w", url, err)
+	}
+
+	currentRevision := filterRefs(refs, ref)
+	return currentRevision, nil
+}
+
 type CheckoutTag struct {
 	Tag               string
 	RecurseSubmodules bool
+	LastRevision      string
 }
 
 func (c *CheckoutTag) Checkout(ctx context.Context, path, url string, opts *git.AuthOptions) (*git.Commit, error) {
@@ -130,6 +145,20 @@ func (c *CheckoutTag) Checkout(ctx context.Context, path, url string, opts *git.
 		return nil, fmt.Errorf("failed to construct auth method with options: %w", err)
 	}
 	ref := plumbing.NewTagReferenceName(c.Tag)
+	// check if previous revision has changed before attempting to clone
+	if c.LastRevision != "" {
+		currentRevision, err := getLastRevision(url, ref, opts, authMethod)
+		if err != nil {
+			return nil, err
+		}
+
+		if currentRevision != "" && currentRevision == c.LastRevision {
+			return nil, git.NoChangesError{
+				Message:          "no changes since last reconcilation",
+				ObservedRevision: currentRevision,
+			}
+		}
+	}
 	repo, err := extgogit.PlainCloneContext(ctx, path, false, &extgogit.CloneOptions{
 		URL:               url,
 		Auth:              authMethod,

pkg/git/gogit/checkout_test.go

@@ -137,13 +137,29 @@ func TestCheckoutTag_Checkout(t *testing.T) {
 		checkoutTag string
 		expectTag   string
 		expectErr   string
+		lastRev     string
+		setLastRev  bool
 	}{
 		{
 			name:        "Tag",
 			tag:         "tag-1",
 			checkoutTag: "tag-1",
 			expectTag:   "tag-1",
 		},
+		{
+			name:        "Skip Tag if last revision hasn't changed",
+			tag:         "tag-2",
+			checkoutTag: "tag-2",
+			setLastRev:  true,
+			expectErr:   "no changes since last reconcilation",
+		},
+		{
+			name:        "Last revision changed",
+			tag:         "tag-3",
+			checkoutTag: "tag-3",
+			expectTag:   "tag-3",
+			lastRev:     "tag-3/<fake-hash>",
+		},
 		{
 			name:        "Annotated",
 			tag:         "annotated",
@@ -168,12 +184,13 @@ func TestCheckoutTag_Checkout(t *testing.T) {
 			}
 
 			var h plumbing.Hash
+			var tagHash *plumbing.Reference
 			if tt.tag != "" {
 				h, err = commitFile(repo, "tag", tt.tag, time.Now())
 				if err != nil {
 					t.Fatal(err)
 				}
-				_, err = tag(repo, h, !tt.annotated, tt.tag, time.Now())
+				tagHash, err = tag(repo, h, !tt.annotated, tt.tag, time.Now())
 				if err != nil {
 					t.Fatal(err)
 				}
@@ -182,10 +199,18 @@ func TestCheckoutTag_Checkout(t *testing.T) {
 			tag := CheckoutTag{
 				Tag: tt.checkoutTag,
 			}
+			if tt.setLastRev {
+				tag.LastRevision = fmt.Sprintf("%s/%s", tt.tag, tagHash.Hash().String())
+			}
+
+			if tt.lastRev != "" {
+				tag.LastRevision = tt.lastRev
+			}
 			tmpDir := t.TempDir()
 
 			cc, err := tag.Checkout(context.TODO(), tmpDir, path, nil)
 			if tt.expectErr != "" {
+				g.Expect(err).ToNot(BeNil())
 				g.Expect(err.Error()).To(ContainSubstring(tt.expectErr))
 				g.Expect(cc).To(BeNil())
 				return