interactively prompt for prune

Author: skarim

cmd/sync.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/cli/go-gh/v2/pkg/prompter"
 	"github.com/github/gh-stack/internal/config"
 	"github.com/github/gh-stack/internal/git"
 	"github.com/github/gh-stack/internal/modify"
@@ -349,7 +350,35 @@ func runSync(cfg *config.Config, opts *syncOptions) error {
 	}
 
 	// --- Step 6: Prune merged branches (optional) ---
-	if opts.prune {
+	doPrune := opts.prune
+	if !doPrune {
+		// --prune was not provided. If interactive, prompt.
+		merged := s.MergedBranches()
+		var prunableCount int
+		for _, b := range merged {
+			if git.BranchExists(b.Branch) {
+				prunableCount++
+			}
+		}
+		if prunableCount > 0 && cfg.IsInteractive() {
+			prompt := fmt.Sprintf("Prune %d merged %s?",
+				prunableCount, plural(prunableCount, "branch", "branches"))
+			confirmed, err := confirmPrune(cfg, prompt, true)
+			if err != nil {
+				if isInterruptError(err) {
+					printInterrupt(cfg)
+					// Save state before exiting so PR sync isn't lost.
+					_ = stack.Save(gitDir, sf)
+					return ErrSilent
+				}
+				// On any other prompt error, skip pruning silently.
+			} else {
+				doPrune = confirmed
+			}
+		}
+	}
+
+	if doPrune {
 		merged := s.MergedBranches()
 		var prunable []string
 		for _, b := range merged {
@@ -395,7 +424,7 @@ func runSync(cfg *config.Config, opts *syncOptions) error {
 			if pruned > 0 {
 				cfg.Successf("Pruned %d merged %s", pruned, plural(pruned, "branch", "branches"))
 			}
-		} else {
+		} else if opts.prune {
 			cfg.Printf("")
 			cfg.Printf("No merged branches to prune")
 		}
@@ -452,3 +481,12 @@ func short(sha string) string {
 	}
 	return sha
 }
+
+// confirmPrune asks the user to confirm pruning via ConfirmFn or a terminal prompt.
+func confirmPrune(cfg *config.Config, prompt string, defaultValue bool) (bool, error) {
+	if cfg.ConfirmFn != nil {
+		return cfg.ConfirmFn(prompt, defaultValue)
+	}
+	p := prompter.New(cfg.In, cfg.Out, cfg.Err)
+	return p.Confirm(prompt, defaultValue)
+}

cmd/sync_test.go

@@ -1286,3 +1286,171 @@ func TestSync_Prune_DeleteFailureContinues(t *testing.T) {
 	assert.Contains(t, output, "Pruned b2 (merged)")
 	assert.Contains(t, output, "Pruned 1 merged branch")
 }
+
+// TestSync_InteractivePrune_PromptsAndPrunes verifies that when running in an
+// interactive terminal without --prune, the user is prompted and merged branches
+// are pruned when they confirm.
+func TestSync_InteractivePrune_PromptsAndPrunes(t *testing.T) {
+	s := stack.Stack{
+		Trunk: stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{
+			{Branch: "b1", PullRequest: &stack.PullRequestRef{Number: 1, Merged: true}},
+			{Branch: "b2"},
+		},
+	}
+
+	tmpDir := t.TempDir()
+	writeStackFile(t, tmpDir, s)
+
+	var deletedBranches []string
+	var promptShown string
+
+	mock := newSyncMock(tmpDir, "b2")
+	mock.BranchExistsFn = func(name string) bool { return true }
+	mock.DeleteBranchFn = func(name string, force bool) error {
+		deletedBranches = append(deletedBranches, name)
+		return nil
+	}
+
+	restore := git.SetOps(mock)
+	defer restore()
+
+	cfg, _, errR := config.NewTestConfig()
+	cfg.ForceInteractive = true
+	cfg.ConfirmFn = func(prompt string, defaultValue bool) (bool, error) {
+		promptShown = prompt
+		assert.True(t, defaultValue, "default should be yes")
+		return true, nil // user confirms
+	}
+
+	cmd := SyncCmd(cfg)
+	// No --prune flag
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	err := cmd.Execute()
+
+	cfg.Err.Close()
+	errOut, _ := io.ReadAll(errR)
+	output := string(errOut)
+
+	assert.NoError(t, err)
+	assert.Contains(t, promptShown, "Prune 1 merged branch")
+	assert.Equal(t, []string{"b1"}, deletedBranches)
+	assert.Contains(t, output, "Pruned b1 (merged)")
+}
+
+// TestSync_InteractivePrune_UserDeclines verifies that when the user declines
+// the prune prompt, no branches are deleted.
+func TestSync_InteractivePrune_UserDeclines(t *testing.T) {
+	s := stack.Stack{
+		Trunk: stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{
+			{Branch: "b1", PullRequest: &stack.PullRequestRef{Number: 1, Merged: true}},
+			{Branch: "b2"},
+		},
+	}
+
+	tmpDir := t.TempDir()
+	writeStackFile(t, tmpDir, s)
+
+	mock := newSyncMock(tmpDir, "b2")
+	mock.BranchExistsFn = func(name string) bool { return true }
+	mock.DeleteBranchFn = func(string, bool) error {
+		t.Fatal("DeleteBranch should not be called when user declines")
+		return nil
+	}
+
+	restore := git.SetOps(mock)
+	defer restore()
+
+	cfg, _, _ := config.NewTestConfig()
+	cfg.ForceInteractive = true
+	cfg.ConfirmFn = func(string, bool) (bool, error) {
+		return false, nil // user declines
+	}
+
+	cmd := SyncCmd(cfg)
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	err := cmd.Execute()
+
+	assert.NoError(t, err)
+}
+
+// TestSync_NonInteractive_NoPrunePrompt verifies that when the terminal is not
+// interactive and --prune is not set, no prompt is shown and no branches are deleted.
+func TestSync_NonInteractive_NoPrunePrompt(t *testing.T) {
+	s := stack.Stack{
+		Trunk: stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{
+			{Branch: "b1", PullRequest: &stack.PullRequestRef{Number: 1, Merged: true}},
+			{Branch: "b2"},
+		},
+	}
+
+	tmpDir := t.TempDir()
+	writeStackFile(t, tmpDir, s)
+
+	mock := newSyncMock(tmpDir, "b2")
+	mock.BranchExistsFn = func(name string) bool { return true }
+	mock.DeleteBranchFn = func(string, bool) error {
+		t.Fatal("DeleteBranch should not be called in non-interactive mode without --prune")
+		return nil
+	}
+
+	restore := git.SetOps(mock)
+	defer restore()
+
+	cfg, _, _ := config.NewTestConfig()
+	// ForceInteractive is false by default — simulates non-interactive/CI/agent
+
+	cmd := SyncCmd(cfg)
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	err := cmd.Execute()
+
+	assert.NoError(t, err)
+}
+
+// TestSync_ExplicitPrune_SkipsPrompt verifies that --prune flag bypasses the
+// interactive prompt and prunes directly.
+func TestSync_ExplicitPrune_SkipsPrompt(t *testing.T) {
+	s := stack.Stack{
+		Trunk: stack.BranchRef{Branch: "main"},
+		Branches: []stack.BranchRef{
+			{Branch: "b1", PullRequest: &stack.PullRequestRef{Number: 1, Merged: true}},
+			{Branch: "b2"},
+		},
+	}
+
+	tmpDir := t.TempDir()
+	writeStackFile(t, tmpDir, s)
+
+	var deletedBranches []string
+
+	mock := newSyncMock(tmpDir, "b2")
+	mock.BranchExistsFn = func(name string) bool { return true }
+	mock.DeleteBranchFn = func(name string, force bool) error {
+		deletedBranches = append(deletedBranches, name)
+		return nil
+	}
+
+	restore := git.SetOps(mock)
+	defer restore()
+
+	cfg, _, _ := config.NewTestConfig()
+	cfg.ForceInteractive = true
+	cfg.ConfirmFn = func(string, bool) (bool, error) {
+		t.Fatal("ConfirmFn should not be called when --prune is explicit")
+		return false, nil
+	}
+
+	cmd := SyncCmd(cfg)
+	cmd.SetArgs([]string{"--prune"})
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+	err := cmd.Execute()
+
+	assert.NoError(t, err)
+	assert.Equal(t, []string{"b1"}, deletedBranches)
+}

internal/config/config.go

@@ -38,6 +38,10 @@ type Config struct {
 	// SelectFn, when non-nil, is called instead of prompting via the
 	// terminal. Used in tests to simulate interactive selection.
 	SelectFn func(prompt, defaultValue string, options []string) (int, error)
+
+	// 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)
 }
 
 // New creates a new Config with terminal-aware output and color support.