input prompter improvements (#98)

* include prefix in branch name input

* custom prompter with colored input text

* minor fix: arrow direction for initialized stack

* fix comment

* handle SetTermMode err

Author: skarim

cmd/add.go

@@ -3,7 +3,6 @@ package cmd
 import (
 	"fmt"
 
-	"github.com/cli/go-gh/v2/pkg/prompter"
 	"github.com/github/gh-stack/internal/branch"
 	"github.com/github/gh-stack/internal/config"
 	"github.com/github/gh-stack/internal/git"
@@ -146,9 +145,14 @@ func runAdd(cfg *config.Config, opts *addOptions, args []string) error {
 		if s.Numbered && s.Prefix != "" {
 			branchName = branch.NextNumberedName(s.Prefix, existingBranches)
 		} else {
-			p := prompter.New(cfg.In, cfg.Out, cfg.Err)
+			// Pre-fill the prompt with the prefix so the user can see
+			// (and optionally edit) the full branch name.
+			prefill := ""
+			if s.Prefix != "" {
+				prefill = s.Prefix + "/"
+			}
 			for {
-				input, err := p.Input("Enter a name for the new branch", "")
+				input, err := inputWithPrefill(cfg, "Enter a name for the new branch:", prefill)
 				if err != nil {
 					if isInterruptError(err) {
 						printInterrupt(cfg)
@@ -160,7 +164,7 @@ func runAdd(cfg *config.Config, opts *addOptions, args []string) error {
 					cfg.Warningf("branch name cannot be empty, please try again")
 					continue
 				}
-				branchName = applyPrefix(cfg, s.Prefix, input)
+				branchName = input
 				break
 			}
 		}

cmd/add_test.go

@@ -321,6 +321,119 @@ func TestAdd_NothingToCommit(t *testing.T) {
 	assert.Contains(t, output, "no changes to commit")
 }
 
+func TestAdd_PromptPrefillsPrefix(t *testing.T) {
+	gitDir := t.TempDir()
+	saveStack(t, gitDir, stack.Stack{
+		Prefix:   "feat",
+		Trunk:    stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{{Branch: "feat/01"}},
+	})
+
+	var createdBranch string
+	restore := git.SetOps(&git.MockOps{
+		GitDirFn:        func() (string, error) { return gitDir, nil },
+		CurrentBranchFn: func() (string, error) { return "feat/01", nil },
+		CreateBranchFn: func(name, base string) error {
+			createdBranch = name
+			return nil
+		},
+		CheckoutBranchFn: func(name string) error { return nil },
+		RevParseFn:       func(ref string) (string, error) { return "abc", nil },
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+
+	var gotPrompt, gotDefault string
+	cfg.InputFn = func(prompt, defaultValue string) (string, error) {
+		gotPrompt = prompt
+		gotDefault = defaultValue
+		return "feat/my-branch", nil
+	}
+
+	err := runAdd(cfg, &addOptions{}, nil)
+	output := collectOutput(cfg, outR, errR)
+
+	require.NoError(t, err)
+	require.NotContains(t, output, "\u2717", "unexpected error")
+	assert.Contains(t, gotPrompt, ":", "prompt should end with a colon")
+	assert.Equal(t, "feat/", gotDefault, "prompt should pre-fill prefix/")
+	assert.Equal(t, "feat/my-branch", createdBranch, "full input should be used as branch name")
+}
+
+func TestAdd_PromptNoPrefixEmptyDefault(t *testing.T) {
+	gitDir := t.TempDir()
+	saveStack(t, gitDir, stack.Stack{
+		Trunk:    stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{{Branch: "b1"}},
+	})
+
+	var createdBranch string
+	restore := git.SetOps(&git.MockOps{
+		GitDirFn:        func() (string, error) { return gitDir, nil },
+		CurrentBranchFn: func() (string, error) { return "b1", nil },
+		CreateBranchFn: func(name, base string) error {
+			createdBranch = name
+			return nil
+		},
+		CheckoutBranchFn: func(name string) error { return nil },
+		RevParseFn:       func(ref string) (string, error) { return "abc", nil },
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+
+	var gotDefault string
+	cfg.InputFn = func(prompt, defaultValue string) (string, error) {
+		gotDefault = defaultValue
+		return "my-branch", nil
+	}
+
+	err := runAdd(cfg, &addOptions{}, nil)
+	output := collectOutput(cfg, outR, errR)
+
+	require.NoError(t, err)
+	require.NotContains(t, output, "\u2717", "unexpected error")
+	assert.Equal(t, "", gotDefault, "prompt should have empty default when no prefix")
+	assert.Equal(t, "my-branch", createdBranch, "input should be used as-is")
+}
+
+func TestAdd_PromptUserModifiesPrefix(t *testing.T) {
+	gitDir := t.TempDir()
+	saveStack(t, gitDir, stack.Stack{
+		Prefix:   "feat",
+		Trunk:    stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{{Branch: "feat/01"}},
+	})
+
+	var createdBranch string
+	restore := git.SetOps(&git.MockOps{
+		GitDirFn:        func() (string, error) { return gitDir, nil },
+		CurrentBranchFn: func() (string, error) { return "feat/01", nil },
+		CreateBranchFn: func(name, base string) error {
+			createdBranch = name
+			return nil
+		},
+		CheckoutBranchFn: func(name string) error { return nil },
+		RevParseFn:       func(ref string) (string, error) { return "abc", nil },
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+
+	cfg.InputFn = func(prompt, defaultValue string) (string, error) {
+		// Simulate user changing the prefix entirely
+		return "custom/other-name", nil
+	}
+
+	err := runAdd(cfg, &addOptions{}, nil)
+	output := collectOutput(cfg, outR, errR)
+
+	require.NoError(t, err)
+	require.NotContains(t, output, "\u2717", "unexpected error")
+	assert.Equal(t, "custom/other-name", createdBranch, "user-modified input should be used verbatim")
+}
+
 func TestAdd_FromTrunk(t *testing.T) {
 	gitDir := t.TempDir()
 	saveStack(t, gitDir, stack.Stack{

cmd/init.go

@@ -159,8 +159,7 @@ func runInit(cfg *config.Config, opts *initOptions) error {
 	} else if opts.numbered {
 		// === NUMBERED PATH (unchanged) ===
 		if opts.prefix == "" && cfg.IsInteractive() {
-			p := prompter.New(cfg.In, cfg.Out, cfg.Err)
-			prefixInput, err := p.Input("Enter a branch prefix (required for --numbered)", "")
+			prefixInput, err := inputWithPrefill(cfg, "Enter a branch prefix (required for --numbered):", "")
 			if err != nil {
 				if isInterruptError(err) {
 					printInterrupt(cfg)
@@ -377,15 +376,15 @@ func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentB
 			branchName = currentBranch
 		} else {
 			// Create a new branch — fall through to input prompt
-			name, err := promptBranchName(cfg, p, opts.prefix)
+			name, err := promptBranchName(cfg, opts.prefix)
 			if err != nil {
 				return nil, false, err
 			}
 			branchName = name
 		}
 	} else {
 		// On trunk or detached HEAD — prompt for name directly
-		name, err := promptBranchName(cfg, p, opts.prefix)
+		name, err := promptBranchName(cfg, opts.prefix)
 		if err != nil {
 			return nil, false, err
 		}
@@ -430,14 +429,16 @@ func runInteractiveInit(cfg *config.Config, sf *stack.StackFile, trunk, currentB
 	return []string{branchName}, wasAdopted, nil
 }
 
-// promptBranchName prompts the user for a branch name, applying the
-// explicit --prefix if set.
-func promptBranchName(cfg *config.Config, p *prompter.Prompter, prefix string) (string, error) {
-	prompt := "What's the name of the first branch?"
+// promptBranchName prompts the user for a branch name, pre-filling the
+// prefix in the input when set so the user can see and edit the full name.
+func promptBranchName(cfg *config.Config, prefix string) (string, error) {
+	prefill := ""
+	prompt := "What's the name of the first branch:"
 	if prefix != "" {
-		prompt = fmt.Sprintf("Enter a name for the first branch (will be prefixed with %s/)", prefix)
+		prompt = "Enter a name for the first branch:"
+		prefill = prefix + "/"
 	}
-	branchName, err := p.Input(prompt, "")
+	branchName, err := inputWithPrefill(cfg, prompt, prefill)
 	if err != nil {
 		if isInterruptError(err) {
 			printInterrupt(cfg)
@@ -451,9 +452,6 @@ func promptBranchName(cfg *config.Config, p *prompter.Prompter, prefix string) (
 		cfg.Errorf("branch name cannot be empty")
 		return "", ErrInvalidArgs
 	}
-	if prefix != "" {
-		branchName = prefix + "/" + branchName
-	}
 	return branchName, nil
 }
 
@@ -484,12 +482,12 @@ func detectPrefix(branches []string) string {
 func printWhatsNext(cfg *config.Config, s *stack.Stack, branches []string, hasAdopted bool, prCount int) {
 	lastBranch := branches[len(branches)-1]
 
-	// Build the chain: main → branch1 → branch2
+	// Build the chain: main ← branch1 ← branch2
 	parts := []string{s.Trunk.Branch}
 	for _, b := range s.Branches {
 		parts = append(parts, b.Branch)
 	}
-	chain := strings.Join(parts, " → ")
+	chain := strings.Join(parts, " ← ")
 
 	// Success line
 	if hasAdopted {

cmd/init_test.go

@@ -581,7 +581,7 @@ func TestInit_WhatsNext_Fresh(t *testing.T) {
 	output := collectOutput(cfg, outR, errR)
 
 	assert.Contains(t, output, "Created stack")
-	assert.Contains(t, output, "main → my-feature")
+	assert.Contains(t, output, "main ← my-feature")
 	assert.Contains(t, output, "top of stack")
 	assert.Contains(t, output, "What's next:")
 	assert.Contains(t, output, "gh stack add")

cmd/submit.go

@@ -281,8 +281,7 @@ func createPR(cfg *config.Config, client github.ClientOps, s *stack.Stack, i int
 	title, commitBody := defaultPRTitleBody(baseBranch, b.Branch)
 	originalTitle := title
 	if !opts.auto && cfg.IsInteractive() {
-		p := prompter.New(cfg.In, cfg.Out, cfg.Err)
-		input, err := p.Input(fmt.Sprintf("Title for PR (branch %s):", b.Branch), title)
+		input, err := inputWithPrefill(cfg, fmt.Sprintf("Title for PR (branch %s):", b.Branch), title)
 		if err != nil {
 			if isInterruptError(err) {
 				return errInterrupt

cmd/utils.go

@@ -14,6 +14,7 @@ import (
 	"github.com/github/gh-stack/internal/git"
 	"github.com/github/gh-stack/internal/github"
 	"github.com/github/gh-stack/internal/stack"
+	"github.com/mgutz/ansi"
 )
 
 // ErrSilent indicates the error has already been printed to the user.
@@ -69,6 +70,49 @@ func printInterrupt(cfg *config.Config) {
 	cfg.Infof("Received interrupt, aborting operation")
 }
 
+// inputWithPrefill prompts the user for text input with the given prefill
+// already editable in the input field. Unlike survey.Input's Default (which
+// shows in parentheses), this places the prefill text directly in the
+// editable line so the user can append to or modify it. The user's input
+// is rendered in cyan for visual distinction from the prompt message.
+func inputWithPrefill(cfg *config.Config, prompt, prefill string) (string, error) {
+	if cfg.InputFn != nil {
+		return cfg.InputFn(prompt, prefill)
+	}
+
+	stdio := terminal.Stdio{In: cfg.In, Out: cfg.Out, Err: cfg.Err}
+	rr := terminal.NewRuneReader(stdio)
+	if err := rr.SetTermMode(); err != nil {
+		return "", fmt.Errorf("failed to set terminal mode: %w", err)
+	}
+	defer func() { _ = rr.RestoreTermMode() }()
+
+	// Render the prompt in survey style: green bold "?" + message
+	icon := "?"
+	useColor := cfg.Terminal.IsColorEnabled()
+	if useColor {
+		icon = ansi.Color("?", "green+hb")
+	}
+	fmt.Fprintf(cfg.Out, "%s %s ", icon, prompt)
+
+	// Set cyan color for the user's input text
+	if useColor {
+		fmt.Fprint(cfg.Out, ansi.ColorCode("cyan"))
+	}
+
+	line, err := rr.ReadLineWithDefault(0, []rune(prefill))
+
+	// Reset color after input
+	if useColor {
+		fmt.Fprint(cfg.Out, ansi.ColorCode("reset"))
+	}
+
+	if err != nil {
+		return "", err
+	}
+	return string(line), nil
+}
+
 // selectPromptPageSize matches the PageSize used by the go-gh prompter.
 const selectPromptPageSize = 20
 

internal/config/config.go

@@ -42,6 +42,10 @@ type Config struct {
 	// ConfirmFn, when non-nil, is called instead of prompting via the
 	// terminal. Used in tests to simulate yes/no confirmation prompts.
 	ConfirmFn func(prompt string, defaultValue bool) (bool, error)
+
+	// InputFn, when non-nil, is called instead of prompting via the
+	// terminal. Used in tests to simulate text input prompts.
+	InputFn func(prompt, defaultValue string) (string, error)
 }
 
 // New creates a new Config with terminal-aware output and color support.