add sparse checkout

cmd/git-init/main.go

@@ -39,6 +39,7 @@ func init() {
 	flag.BoolVar(&fetchSpec.Submodules, "submodules", true, "Initialize and fetch Git submodules")
 	flag.UintVar(&fetchSpec.Depth, "depth", 1, "Perform a shallow clone to this depth")
 	flag.StringVar(&terminationMessagePath, "terminationMessagePath", "/tekton/termination", "Location of file containing termination message")
+	flag.StringVar(&fetchSpec.SparseCheckoutDirectories, "sparseCheckoutDirectories", "", "String of directory patterns separated by a comma")
 }
 
 func main() {

pkg/git/git.go

@@ -59,16 +59,17 @@ func run(logger *zap.SugaredLogger, dir string, args ...string) (string, error)
 
 // FetchSpec describes how to initialize and fetch from a Git repository.
 type FetchSpec struct {
-	URL        string
-	Revision   string
-	Refspec    string
-	Path       string
-	Depth      uint
-	Submodules bool
-	SSLVerify  bool
-	HTTPProxy  string
-	HTTPSProxy string
-	NOProxy    string
+	URL                       string
+	Revision                  string
+	Refspec                   string
+	Path                      string
+	Depth                     uint
+	Submodules                bool
+	SSLVerify                 bool
+	HTTPProxy                 string
+	HTTPSProxy                string
+	NOProxy                   string
+	SparseCheckoutDirectories string
 }
 
 // Fetch fetches the specified git repository at the revision into path, using the refspec to fetch if provided.
@@ -88,6 +89,9 @@ func Fetch(logger *zap.SugaredLogger, spec FetchSpec) error {
 	} else if _, err := run(logger, "", "init"); err != nil {
 		return err
 	}
+	if err := configSparseCheckout(logger, spec); err != nil {
+		return err
+	}
 	trimmedURL := strings.TrimSpace(spec.URL)
 	if _, err := run(logger, "", "remote", "add", "origin", trimmedURL); err != nil {
 		return err
@@ -281,3 +285,36 @@ func ValidateGitSSHURLFormat(url string) bool {
 	}
 	return false
 }
+
+func configSparseCheckout(logger *zap.SugaredLogger, spec FetchSpec) error {
+	if spec.SparseCheckoutDirectories != "" {
+		if _, err := run(logger, "", "config", "core.sparsecheckout", "true"); err != nil {
+			return err
+		}
+
+		dirPatterns := strings.Split(spec.SparseCheckoutDirectories, ",")
+
+		cwd, err := os.Getwd()
+		if err != nil {
+			logger.Errorf("failed to get current directory: %v", err)
+			return err
+		}
+		file, err := os.OpenFile(filepath.Join(cwd, ".git/info/sparse-checkout"), os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			logger.Errorf("failed to open sparse-checkout file: %v", err)
+			return err
+		}
+		for _, pattern := range dirPatterns {
+			if _, err := file.WriteString(pattern + "\n"); err != nil {
+				file.Close()
+				logger.Errorf("failed to write to sparse-checkout file: %v", err)
+				return err
+			}
+		}
+		if err := file.Close(); err != nil {
+			logger.Errorf("failed to close sparse-checkout file: %v", err)
+			return err
+		}
+	}
+	return nil
+}

pkg/git/git_test.go

@@ -16,11 +16,13 @@ limitations under the License.
 package git
 
 import (
+	"bufio"
 	"io/ioutil"
 	"os"
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zaptest/observer"
 )
@@ -175,16 +177,34 @@ func TestFetch(t *testing.T) {
 			logMessage: "Successfully cloned",
 			wantErr:    false,
 			spec: FetchSpec{
-				URL:        "",
-				Revision:   "",
-				Refspec:    "",
-				Path:       "",
-				Depth:      0,
-				Submodules: false,
-				SSLVerify:  false,
-				HTTPProxy:  "",
-				HTTPSProxy: "",
-				NOProxy:    "",
+				URL:                       "",
+				Revision:                  "",
+				Refspec:                   "",
+				Path:                      "",
+				Depth:                     0,
+				Submodules:                false,
+				SSLVerify:                 false,
+				HTTPProxy:                 "",
+				HTTPSProxy:                "",
+				NOProxy:                   "",
+				SparseCheckoutDirectories: "",
+			},
+		}, {
+			name:       "test-clone-with-sparse-checkout",
+			logMessage: "Successfully cloned",
+			wantErr:    false,
+			spec: FetchSpec{
+				URL:                       "",
+				Revision:                  "",
+				Refspec:                   "",
+				Path:                      "",
+				Depth:                     0,
+				Submodules:                false,
+				SSLVerify:                 false,
+				HTTPProxy:                 "",
+				HTTPSProxy:                "",
+				NOProxy:                   "",
+				SparseCheckoutDirectories: "a,b/c",
 			},
 		},
 	}
@@ -206,6 +226,27 @@ func TestFetch(t *testing.T) {
 				t.Errorf("Fetch() error = %v, wantErr %v", err, tt.wantErr)
 			}
 
+			if tt.spec.SparseCheckoutDirectories != "" {
+				dirPatterns := strings.Split(tt.spec.SparseCheckoutDirectories, ",")
+
+				sparseFile, err := os.Open(".git/info/sparse-checkout")
+				if err != nil {
+					t.Fatal("Unable to read sparse-checkout file")
+				}
+				defer sparseFile.Close()
+
+				var sparsePatterns []string
+
+				scanner := bufio.NewScanner(sparseFile)
+				for scanner.Scan() {
+					sparsePatterns = append(sparsePatterns, scanner.Text())
+				}
+
+				if cmp.Diff(dirPatterns, sparsePatterns) != "" {
+					t.Errorf("directory patterns and sparse-checkout patterns do not match")
+				}
+			}
+
 			if tt.logMessage != "" {
 				takeAll := log.TakeAll()
 				if len(takeAll) == 0 {