address review comments

Author: skarim

cmd/init.go

@@ -180,7 +180,9 @@ func runInit(cfg *config.Config, opts *initOptions) error {
 			cfg.Errorf("branch %q already exists in a stack", branchName)
 			return ErrInvalidArgs
 		}
-		if !git.BranchExists(branchName) {
+		if git.BranchExists(branchName) {
+			adopted[branchName] = true
+		} else {
 			if err := git.CreateBranch(branchName, trunk); err != nil {
 				cfg.Errorf("creating branch %s: %s", branchName, err)
 				return ErrSilent
@@ -195,10 +197,14 @@ func runInit(cfg *config.Config, opts *initOptions) error {
 			return ErrInvalidArgs
 		}
 
-		branches, err = runInteractiveInit(cfg, sf, trunk, currentBranch, opts)
+		var interactiveAdopted bool
+		branches, interactiveAdopted, err = runInteractiveInit(cfg, sf, trunk, currentBranch, opts)
 		if err != nil {
 			return err
 		}
+		if interactiveAdopted {
+			adopted[branches[0]] = true
+		}
 	}
 
 	// --- Build stack ---
@@ -285,6 +291,13 @@ func resolveArgBranches(cfg *config.Config, opts *initOptions, sf *stack.StackFi
 		if opts.prefix != "" {
 			b = opts.prefix + "/" + b
 		}
+
+		// Validate ref name before checking existence or creating
+		if err := git.ValidateRefName(b); err != nil {
+			cfg.Errorf("invalid branch name %q: must be a valid git ref", b)
+			return nil, nil, ErrInvalidArgs
+		}
+
 		exists := git.BranchExists(b)
 
 		if err := sf.ValidateNoDuplicateBranch(b); err != nil {
@@ -318,8 +331,9 @@ func resolveArgBranches(cfg *config.Config, opts *initOptions, sf *stack.StackFi
 
 // runInteractiveInit runs the interactive init flow: prints hint about
 // multi-branch args, offers current branch or new branch, then runs
-// prefix detection.
-func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentBranch string, opts *initOptions) ([]string, error) {
+// prefix detection. Returns the branches and whether the branch was adopted
+// (already existed).
+func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentBranch string, opts *initOptions) ([]string, bool, error) {
 	p := prompter.New(cfg.In, cfg.Out, cfg.Err)
 
 	cfg.Printf("Initializing a stack from %s.", trunk)
@@ -348,45 +362,48 @@ func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentB
 					clearSelectPrompt(cfg, len(options))
 				}
 				printInterrupt(cfg)
-				return nil, ErrSilent
+				return nil, false, ErrSilent
 			}
 			cfg.Errorf("failed to read selection: %s", err)
-			return nil, ErrSilent
+			return nil, false, ErrSilent
 		}
 
 		if selected == 0 {
 			// Use current branch
 			if err := sf.ValidateNoDuplicateBranch(currentBranch); err != nil {
 				cfg.Errorf("branch %q already exists in a stack", currentBranch)
-				return nil, ErrInvalidArgs
+				return nil, false, ErrInvalidArgs
 			}
 			branchName = currentBranch
 		} else {
 			// Create a new branch — fall through to input prompt
 			name, err := promptBranchName(cfg, p, opts.prefix)
 			if err != nil {
-				return nil, err
+				return nil, false, err
 			}
 			branchName = name
 		}
 	} else {
 		// On trunk or detached HEAD — prompt for name directly
 		name, err := promptBranchName(cfg, p, opts.prefix)
 		if err != nil {
-			return nil, err
+			return nil, false, err
 		}
 		branchName = name
 	}
 
-	// Validate and create branch
+	// Validate and create branch (track whether it was adopted)
+	wasAdopted := false
 	if err := sf.ValidateNoDuplicateBranch(branchName); err != nil {
 		cfg.Errorf("branch %q already exists in a stack", branchName)
-		return nil, ErrInvalidArgs
+		return nil, false, ErrInvalidArgs
 	}
-	if !git.BranchExists(branchName) {
+	if git.BranchExists(branchName) {
+		wasAdopted = true
+	} else {
 		if err := git.CreateBranch(branchName, trunk); err != nil {
 			cfg.Errorf("creating branch %s: %s", branchName, err)
-			return nil, ErrSilent
+			return nil, false, ErrSilent
 		}
 	}
 
@@ -401,7 +418,7 @@ func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentB
 			if err != nil {
 				if isInterruptError(err) {
 					printInterrupt(cfg)
-					return nil, ErrSilent
+					return nil, false, ErrSilent
 				}
 				// Not fatal — just skip prefix
 			} else if usePrefix {
@@ -410,7 +427,7 @@ func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentB
 		}
 	}
 
-	return []string{branchName}, nil
+	return []string{branchName}, wasAdopted, nil
 }
 
 // promptBranchName prompts the user for a branch name, applying the

cmd/init_test.go

@@ -721,6 +721,8 @@ func TestInit_Interactive_OnFeatureBranch_UseCurrent(t *testing.T) {
 
 	require.NoError(t, err)
 	assert.Contains(t, output, "Initializing a stack from main")
+	// Branch already exists → should be treated as adopted
+	assert.Contains(t, output, "Adopted")
 
 	sf, _ := stack.Load(gitDir)
 	require.Len(t, sf.Stacks, 1)
@@ -764,6 +766,36 @@ func TestInit_TwoPassValidation_NoBranchCreatedOnError(t *testing.T) {
 	assert.Empty(t, created, "no branches should be created when later arg fails validation")
 }
 
+func TestInit_TwoPassValidation_InvalidRefName(t *testing.T) {
+	// Verify that an invalid ref name in the args list prevents any branch creation
+	gitDir := t.TempDir()
+	var created []string
+	restore := git.SetOps(&git.MockOps{
+		GitDirFn:        func() (string, error) { return gitDir, nil },
+		DefaultBranchFn: func() (string, error) { return "main", nil },
+		CurrentBranchFn: func() (string, error) { return "main", nil },
+		ValidateRefNameFn: func(name string) error {
+			if name == "invalid..name" {
+				return fmt.Errorf("invalid ref name: %s", name)
+			}
+			return nil
+		},
+		CreateBranchFn: func(name, base string) error {
+			created = append(created, name)
+			return nil
+		},
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+	err := runInit(cfg, &initOptions{branches: []string{"valid-branch", "invalid..name", "another-branch"}})
+	output := collectOutput(cfg, outR, errR)
+
+	assert.ErrorIs(t, err, ErrInvalidArgs)
+	assert.Contains(t, output, "invalid branch name")
+	assert.Empty(t, created, "no branches should be created when an arg has an invalid ref name")
+}
+
 func TestDetectPrefix(t *testing.T) {
 	tests := []struct {
 		name     string