remove unnecessary push when rendering to local path (#272)

Signed-off-by: Kent Rancourt <kent.rancourt@gmail.com>

branches.go

@@ -80,12 +80,12 @@ func switchToTargetBranch(rc requestContext) error {
 	logger := rc.logger.WithField("targetBranch", rc.request.TargetBranch)
 
 	// Check if the target branch exists on the remote
-	targetBranchExists, err := rc.repo.RemoteBranchExists(rc.request.TargetBranch)
+	remoteTargetBranchExists, err := rc.repo.RemoteBranchExists(rc.request.TargetBranch)
 	if err != nil {
-		return fmt.Errorf("error checking for existence of target branch: %w", err)
+		return fmt.Errorf("error checking for existence of remote target branch: %w", err)
 	}
 
-	if targetBranchExists {
+	if remoteTargetBranchExists {
 		logger.Debug("target branch exists on remote")
 		if err = rc.repo.Fetch(); err != nil {
 			return fmt.Errorf("error fetching from remote: %w", err)
@@ -103,10 +103,31 @@ func switchToTargetBranch(rc requestContext) error {
 	}
 
 	logger.Debug("target branch does not exist on remote")
-	if err = rc.repo.CreateOrphanedBranch(rc.request.TargetBranch); err != nil {
-		return fmt.Errorf("error creating new target branch: %w", err)
+
+	// Check if the target branch exists locally
+	localTargetBranchExists, err := rc.repo.LocalBranchExists(rc.request.TargetBranch)
+	if err != nil {
+		return fmt.Errorf("error checking for existence of local target branch: %w", err)
 	}
-	logger.Debug("created target branch")
+
+	if localTargetBranchExists {
+		logger.Debug("target branch exists locally")
+		if err = rc.repo.Checkout(rc.request.TargetBranch); err != nil {
+			return fmt.Errorf("error checking out target branch: %w", err)
+		}
+		logger.Debug("checked out target branch")
+	} else {
+		logger.Debug("target branch does not exist locally")
+		if err = rc.repo.CreateOrphanedBranch(rc.request.TargetBranch); err != nil {
+			return fmt.Errorf("error creating new target branch: %w", err)
+		}
+		logger.Debug("created target branch locally")
+	}
+
+	if rc.request.LocalOutPath != "" {
+		return nil // There's no need to push the new branch to the remote
+	}
+
 	if err = rc.repo.Commit(
 		"Initial commit",
 		&git.CommitOptions{

docs/docs/30-how-to-guides/30-docker-image.md

@@ -17,7 +17,7 @@ easiest option for experimenting locally with Kargo Render!
 Example usage:
 
 ```shell
-docker run -it ghcr.io/akuity/kargo-render:v0.1.0-rc.38 \
+docker run -it ghcr.io/akuity/kargo-render:v0.1.0-rc.39 \
   --repo https://github.com/<your GitHub handle>/kargo-render-demo-deploy \
   --repo-username <your GitHub handle> \
   --repo-password <a GitHub personal access token> \

pkg/git/git.go

@@ -68,6 +68,8 @@ type Repo interface {
 	// LastCommitID returns the ID (sha) of the most recent commit to the current
 	// branch.
 	LastCommitID() (string, error)
+	// LocalBranchExists returns a bool indicating if the specified branch exists.
+	LocalBranchExists(branch string) (bool, error)
 	// CommitMessage returns the text of the most recent commit message associated
 	// with the specified commit ID.
 	CommitMessage(id string) (string, error)
@@ -366,6 +368,21 @@ func (r *repo) LastCommitID() (string, error) {
 	return strings.TrimSpace(string(shaBytes)), nil
 }
 
+func (r *repo) LocalBranchExists(branch string) (bool, error) {
+	resBytes, err := libExec.Exec(r.buildCommand(
+		"branch",
+		"--list",
+		branch,
+	))
+	if err != nil {
+		return false,
+			fmt.Errorf("error checking for existence of local branch %q: %w", branch, err)
+	}
+	return strings.TrimSpace(
+		strings.Replace(string(resBytes), "*", "", 1),
+	) == branch, nil
+}
+
 func (r *repo) CommitMessage(id string) (string, error) {
 	msgBytes, err := libExec.Exec(
 		r.buildCommand("log", "-n", "1", "--pretty=format:%s", id),

pkg/git/git_test.go

@@ -168,12 +168,28 @@ func TestRepo(t *testing.T) {
 		require.NoError(t, err)
 	})
 
+	testBranch := fmt.Sprintf("test-branch-%s", uuid.NewString())
+	err = r.CreateChildBranch(testBranch)
+	require.NoError(t, err)
+
 	t.Run("can create a child branch", func(t *testing.T) {
-		testBranch := fmt.Sprintf("test-branch-%s", uuid.NewString())
-		err = r.CreateChildBranch(testBranch)
 		require.NoError(t, err)
 	})
 
+	t.Run("can check if local branch exists -- negative result", func(t *testing.T) {
+		var exists bool
+		exists, err = r.LocalBranchExists("branch-that-does-not-exist")
+		require.NoError(t, err)
+		require.False(t, exists)
+	})
+
+	t.Run("can check if local branch exists -- positive result", func(t *testing.T) {
+		var exists bool
+		exists, err = r.LocalBranchExists(testBranch)
+		require.NoError(t, err)
+		require.True(t, exists)
+	})
+
 	err = os.WriteFile(fmt.Sprintf("%s/%s", r.WorkingDir(), "test.txt"), []byte("bar"), 0600)
 	require.NoError(t, err)