git: fix pulling commit SHA only referenced from a tag

On commit SHA input we currently do a full fetch of
remote so we can pick up the commit by SHA later. This
only pulls in tags that are also part of branches. Extra
flag is needed to also get the tags that are not part of
branches.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

source/git/source_test.go

@@ -217,6 +217,72 @@ func testFetchBySHA(t *testing.T, keepGitDir bool) {
 	require.Equal(t, "subcontents\n", string(dt))
 }
 
+func TestFetchUnreferencedTagSha(t *testing.T) {
+	testFetchUnreferencedTagSha(t, false)
+}
+
+func TestFetchUnreferencedTagShaKeepGitDir(t *testing.T) {
+	testFetchUnreferencedTagSha(t, true)
+}
+
+// testFetchUnreferencedTagSha tests fetching a SHA that points to a tag that is not reachable from any branch.
+func testFetchUnreferencedTagSha(t *testing.T, keepGitDir bool) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Depends on unimplemented containerd bind-mount support on Windows")
+	}
+
+	t.Parallel()
+	ctx := namespaces.WithNamespace(context.Background(), "buildkit-test")
+	ctx = logProgressStreams(ctx, t)
+
+	gs := setupGitSource(t, t.TempDir())
+
+	repo := setupGitRepo(t)
+
+	cmd := exec.Command("git", "rev-parse", "v1.2.3-special")
+	cmd.Dir = repo.mainPath
+
+	out, err := cmd.Output()
+	require.NoError(t, err)
+
+	sha := strings.TrimSpace(string(out))
+	require.Equal(t, 40, len(sha))
+
+	id := &GitIdentifier{Remote: repo.mainURL, Ref: sha, KeepGitDir: keepGitDir}
+
+	g, err := gs.Resolve(ctx, id, nil, nil)
+	require.NoError(t, err)
+
+	key1, pin1, _, done, err := g.CacheKey(ctx, nil, 0)
+	require.NoError(t, err)
+	require.True(t, done)
+
+	expLen := 40
+	if keepGitDir {
+		expLen += 4
+	}
+
+	require.Equal(t, expLen, len(key1))
+	require.Equal(t, 40, len(pin1))
+
+	ref1, err := g.Snapshot(ctx, nil)
+	require.NoError(t, err)
+	defer ref1.Release(context.TODO())
+
+	mount, err := ref1.Mount(ctx, true, nil)
+	require.NoError(t, err)
+
+	lm := snapshot.LocalMounter(mount)
+	dir, err := lm.Mount()
+	require.NoError(t, err)
+	defer lm.Unmount()
+
+	dt, err := os.ReadFile(filepath.Join(dir, "bar"))
+	require.NoError(t, err)
+
+	require.Equal(t, "foo\n", string(dt))
+}
+
 func TestFetchByTag(t *testing.T) {
 	testFetchByTag(t, "lightweight-tag", "third", false, true, false)
 }
@@ -610,6 +676,13 @@ func setupGitRepo(t *testing.T) gitRepoFixture {
 		"git add subfile",
 		"git commit -m initial",
 	)
+	// * (refs/heads/feature) withsub
+	// * feature
+	// * (HEAD -> refs/heads/master, tag: refs/tags/lightweight-tag) third
+	// | * (tag: refs/tags/v1.2.3-special) tagonly-leaf
+	// |/
+	// * (tag: refs/tags/v1.2.3) second
+	// * (tag: refs/tags/a/v1.2.3) initial
 	runShell(t, fixture.mainPath,
 		"git -c init.defaultBranch=master init",
 		"git config --local user.email test",
@@ -622,6 +695,12 @@ func setupGitRepo(t *testing.T) gitRepoFixture {
 		"git add def",
 		"git commit -m second",
 		"git tag -a -m \"this is an annotated tag\" v1.2.3",
+		"echo foo > bar",
+		"git add bar",
+		"git commit -m tagonly-leaf",
+		"git tag --no-sign v1.2.3-special",
+		// switch master back to v1.2.3
+		"git checkout -B master v1.2.3",
 		"echo sbb > foo13",
 		"git add foo13",
 		"git commit -m third",
@@ -635,6 +714,7 @@ func setupGitRepo(t *testing.T) gitRepoFixture {
 		"git add -A",
 		"git commit -m withsub",
 		"git checkout master",
+		// "git log --oneline --graph --decorate=full --all",
 	)
 	return fixture
 }