make warehouse do shallow, single-branch clones

internal/controller/git/git.go

@@ -95,6 +95,19 @@ type repo struct {
 	currentBranch string
 }
 
+// CloneOptions represents options for cloning a git repository.
+type CloneOptions struct {
+	// Branch is the name of the branch to clone. If not specified, the default
+	// branch will be cloned.
+	Branch string
+	// SingleBranch indicates whether the clone should be a single-branch clone.
+	SingleBranch bool
+	// Shallow indicates whether the clone should be with a depth of 1. This is
+	// useful for speeding up the cloning process when all we care about is the
+	// latest commit from a single branch.
+	Shallow bool
+}
+
 // Clone produces a local clone of the remote git repository at the specified
 // URL and returns an implementation of the Repo interface that is stateful and
 // NOT suitable for use across multiple goroutines. This function will also
@@ -103,6 +116,7 @@ type repo struct {
 func Clone(
 	repoURL string,
 	repoCreds RepoCredentials,
+	opts *CloneOptions,
 ) (Repo, error) {
 	homeDir, err := os.MkdirTemp("", "")
 	if err != nil {
@@ -120,7 +134,7 @@ func Clone(
 	if err = r.setupAuth(repoCreds); err != nil {
 		return nil, err
 	}
-	return r, r.clone()
+	return r, r.clone(opts)
 }
 
 func (r *repo) AddAll() error {
@@ -140,9 +154,25 @@ func (r *repo) Clean() error {
 	return errors.Wrapf(err, "error cleaning branch %q", r.currentBranch)
 }
 
-func (r *repo) clone() error {
-	r.currentBranch = "HEAD"
-	cmd := r.buildCommand("clone", "--no-tags", r.url, r.dir)
+func (r *repo) clone(opts *CloneOptions) error {
+	if opts == nil {
+		opts = &CloneOptions{}
+	}
+	args := []string{"clone", "--no-tags"}
+	if opts.Branch != "" {
+		args = append(args, "--branch", opts.Branch)
+		r.currentBranch = opts.Branch
+	} else {
+		r.currentBranch = "HEAD"
+	}
+	if opts.SingleBranch {
+		args = append(args, "--single-branch")
+	}
+	if opts.Shallow {
+		args = append(args, "--depth=1")
+	}
+	args = append(args, r.url, r.dir)
+	cmd := r.buildCommand(args...)
 	cmd.Dir = r.homeDir // Override the cmd.Dir that's set by r.buildCommand()
 	_, err := libExec.Exec(cmd)
 	return errors.Wrapf(

internal/controller/promotion/git.go

@@ -243,7 +243,7 @@ func (g *gitMechanism) gitCommit(
 	if creds == nil {
 		creds = &git.RepoCredentials{}
 	}
-	repo, err := git.Clone(update.RepoURL, *creds)
+	repo, err := git.Clone(update.RepoURL, *creds, nil)
 	if err != nil {
 		return "", errors.Wrapf(err, "error cloning git repo %q", update.RepoURL)
 	}

internal/controller/warehouses/git.go

@@ -84,19 +84,17 @@ func getLatestCommitMeta(
 	if creds == nil {
 		creds = &git.RepoCredentials{}
 	}
-	repo, err := git.Clone(repoURL, *creds)
+	repo, err := git.Clone(
+		repoURL,
+		*creds,
+		&git.CloneOptions{
+			Branch:       branch,
+			SingleBranch: true,
+			Shallow:      true,
+		},
+	)
 	if err != nil {
 		return nil, errors.Wrapf(err, "error cloning git repo %q", repoURL)
-
-	}
-	if branch != "" {
-		if err = repo.Checkout(branch); err != nil {
-			return nil, errors.Wrapf(
-				err,
-				"error checking out branch %q from git repo",
-				repoURL,
-			)
-		}
 	}
 	var gm gitMeta
 	gm.Commit, err = repo.LastCommitID()

internal/controller/warehouses/git_test.go

@@ -155,17 +155,6 @@ func TestGetLatestCommitID(t *testing.T) {
 				require.Contains(t, err.Error(), "error cloning git repo")
 			},
 		},
-
-		{
-			name:    "error checking out branch",
-			repoURL: "https://github.com/akuity/kargo.git",
-			branch:  "bogus", // This should force a failure
-			assertions: func(_ *gitMeta, err error) {
-				require.Error(t, err)
-				require.Contains(t, err.Error(), "error checking out branch")
-			},
-		},
-
 		{
 			name:    "success",
 			repoURL: "https://github.com/akuity/kargo.git",