support adopting branches with PRs

Author: skarim

cmd/init.go

@@ -174,25 +174,6 @@ func runInit(cfg *config.Config, opts *initOptions) error {
 			}
 		}
 		branches = opts.branches
-
-		// Check if any adopted branches already have PRs on GitHub.
-		// If offline or unable to create client, skip silently.
-		if client, clientErr := cfg.GitHubClient(); clientErr == nil {
-			for _, b := range branches {
-				pr, err := client.FindAnyPRForBranch(b)
-				if err != nil {
-					continue
-				}
-				if pr != nil {
-					state := "open"
-					if pr.Merged {
-						state = "merged"
-					}
-					cfg.Errorf("branch %q already has a %s PR (#%d: %s)", b, state, pr.Number, pr.URL)
-					return ErrInvalidArgs
-				}
-			}
-		}
 	} else if len(opts.branches) > 0 {
 		// Explicit branch names provided — apply prefix and create them
 		prefixed := make([]string, 0, len(opts.branches))
@@ -323,8 +304,28 @@ func runInit(cfg *config.Config, opts *initOptions) error {
 
 	sf.AddStack(newStack)
 
-	// Sync PR state for adopted branches
-	syncStackPRs(cfg, &sf.Stacks[len(sf.Stacks)-1])
+	// Discover existing PRs for the new stack's branches.
+	// For adopt, only record open/draft PRs (ignore closed/merged).
+	// For non-adopt, use the standard sync which also detects merges.
+	newStack_ := &sf.Stacks[len(sf.Stacks)-1]
+	if opts.adopt {
+		if client, clientErr := cfg.GitHubClient(); clientErr == nil {
+			for i := range newStack_.Branches {
+				b := &newStack_.Branches[i]
+				pr, err := client.FindPRForBranch(b.Branch)
+				if err != nil || pr == nil {
+					continue
+				}
+				b.PullRequest = &stack.PullRequestRef{
+					Number: pr.Number,
+					ID:     pr.ID,
+					URL:    pr.URL,
+				}
+			}
+		}
+	} else {
+		syncStackPRs(cfg, newStack_)
+	}
 
 	if err := stack.Save(gitDir, sf); err != nil {
 		return handleSaveError(cfg, err)

cmd/init_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/github/gh-stack/internal/config"
 	"github.com/github/gh-stack/internal/git"
+	"github.com/github/gh-stack/internal/github"
 	"github.com/github/gh-stack/internal/stack"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -290,3 +291,91 @@ func TestInit_MultipleBranches_CreatesAll(t *testing.T) {
 	names := sf.Stacks[0].BranchNames()
 	assert.Equal(t, []string{"b1", "b2", "b3"}, names)
 }
+
+func TestInit_AdoptWithExistingOpenPR(t *testing.T) {
+	gitDir := t.TempDir()
+	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 },
+		BranchExistsFn:  func(string) bool { return true },
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+	cfg.GitHubClientOverride = &github.MockClient{
+		FindPRForBranchFn: func(branch string) (*github.PullRequest, error) {
+			if branch == "b1" {
+				return &github.PullRequest{
+					Number:      42,
+					ID:          "PR_42",
+					URL:         "https://github.com/owner/repo/pull/42",
+					State:       "OPEN",
+					HeadRefName: "b1",
+				}, nil
+			}
+			return nil, nil
+		},
+	}
+
+	err := runInit(cfg, &initOptions{
+		branches: []string{"b1", "b2"},
+		adopt:    true,
+	})
+	output := collectOutput(cfg, outR, errR)
+
+	require.NoError(t, err, "adopt should succeed even when branch has an open PR")
+	require.NotContains(t, output, "\u2717", "unexpected error in output")
+
+	sf, err := stack.Load(gitDir)
+	require.NoError(t, err, "loading stack")
+	require.Len(t, sf.Stacks, 1)
+
+	// b1 should have the open PR recorded
+	b1 := sf.Stacks[0].Branches[0]
+	require.NotNil(t, b1.PullRequest, "open PR should be recorded")
+	assert.Equal(t, 42, b1.PullRequest.Number)
+	assert.Equal(t, "https://github.com/owner/repo/pull/42", b1.PullRequest.URL)
+
+	// b2 should have no PR
+	b2 := sf.Stacks[0].Branches[1]
+	assert.Nil(t, b2.PullRequest, "branch without PR should have nil PullRequest")
+}
+
+func TestInit_AdoptIgnoresClosedAndMergedPRs(t *testing.T) {
+	gitDir := t.TempDir()
+	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 },
+		BranchExistsFn:  func(string) bool { return true },
+	})
+	defer restore()
+
+	cfg, outR, errR := config.NewTestConfig()
+	// FindPRForBranch only returns OPEN PRs — closed/merged PRs won't be
+	// returned by the API, so the mock returns nil for all branches.
+	cfg.GitHubClientOverride = &github.MockClient{
+		FindPRForBranchFn: func(branch string) (*github.PullRequest, error) {
+			return nil, nil
+		},
+	}
+
+	err := runInit(cfg, &initOptions{
+		branches: []string{"b1", "b2"},
+		adopt:    true,
+	})
+	output := collectOutput(cfg, outR, errR)
+
+	require.NoError(t, err, "adopt should succeed when branches have closed/merged PRs")
+	require.NotContains(t, output, "\u2717", "unexpected error in output")
+
+	sf, err := stack.Load(gitDir)
+	require.NoError(t, err, "loading stack")
+	require.Len(t, sf.Stacks, 1)
+
+	// Neither branch should have a PR recorded (closed/merged are filtered out)
+	for _, b := range sf.Stacks[0].Branches {
+		assert.Nil(t, b.PullRequest, "closed/merged PRs should not be recorded for branch %s", b.Branch)
+	}
+}