Checkout the branch you were on if an error happens.

When you do `opp pr` and we need to rebase and the rebase fails,
it's better if opp checks out the commit you were on before.

cmd/pr.go

@@ -75,6 +75,10 @@ func PrCommand(repo *core.Repo, gh func(context.Context) core.Gh) *cli.Command {
 			},
 		},
 		Action: func(cCtx *cli.Context) error {
+			initialRef, err := repo.Head()
+			if err != nil {
+				return err
+			}
 			pr := create{Repo: repo, Github: gh(cCtx.Context)}
 			args, err := pr.SanitizeArgs(cCtx)
 			if err != nil {
@@ -83,6 +87,7 @@ func PrCommand(repo *core.Repo, gh func(context.Context) core.Gh) *cli.Command {
 			if args.NeedsRebase {
 				newArgs, err := pr.RebasePrCommits(cCtx.Context, args)
 				if err != nil {
+					repo.CheckoutRef(initialRef)
 					return err
 				}
 				args = newArgs
@@ -95,7 +100,7 @@ func PrCommand(repo *core.Repo, gh func(context.Context) core.Gh) *cli.Command {
 			if args.CheckoutPr {
 				return repo.Checkout(localPr)
 			}
-			return nil
+			return repo.CheckoutRef(initialRef)
 		},
 	}
 
@@ -202,12 +207,15 @@ func HeadCommit(repo *core.Repo, args cli.Args) (plumbing.Hash, error) {
 // since HEAD will be detached after the rebase.
 func (c *create) RebasePrCommits(ctx context.Context, previousArgs *args) (*args, error) {
 	// Careful ! The first commit is the child-most one, not the other way around.
+	err := c.Repo.DetachHead(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("could not detach head: %w", err)
+	}
 	if previousArgs.Interactive {
 		fmt.Println("Choose what commits you want to include in this PR")
 		if !c.Repo.TryRebaseOntoSilently(
 			ctx,
 			previousArgs.Commits[len(previousArgs.Commits)-1].Hash,
-			previousArgs.Commits[0].Hash,
 			previousArgs.AncestorBranch,
 			true,
 		) {
@@ -221,7 +229,6 @@ func (c *create) RebasePrCommits(ctx context.Context, previousArgs *args) (*args
 		if !c.Repo.TryRebaseOntoSilently(
 			ctx,
 			previousArgs.Commits[len(previousArgs.Commits)-1].Hash,
-			previousArgs.Commits[0].Hash,
 			previousArgs.AncestorBranch,
 			false,
 		) {
@@ -300,7 +307,14 @@ func (c *create) createLocalBranchForPr(number int, hash plumbing.Hash, ancestor
 	c.Repo.Storer.SetReference(plumbing.NewHashReference(ref, hash))
 }
 
-func (c *create) create(ctx context.Context, hash plumbing.Hash, ancestor core.Branch, title string, body string, draft bool) (int, error) {
+func (c *create) create(
+	ctx context.Context,
+	hash plumbing.Hash,
+	ancestor core.Branch,
+	title string,
+	body string,
+	draft bool,
+) (int, error) {
 	for attempts := 0; attempts < 3; attempts++ {
 		pr, err := c.createOnce(ctx, hash, ancestor, title, body, draft)
 		if err == nil {
@@ -316,7 +330,14 @@ func (c *create) create(ctx context.Context, hash plumbing.Hash, ancestor core.B
 	return 0, ErrLostPrCreationRaceConditionMultipleTimes
 }
 
-func (c *create) createOnce(ctx context.Context, hash plumbing.Hash, ancestor core.Branch, title string, body string, draft bool) (int, error) {
+func (c *create) createOnce(
+	ctx context.Context,
+	hash plumbing.Hash,
+	ancestor core.Branch,
+	title string,
+	body string,
+	draft bool,
+) (int, error) {
 	ctx, cancel := context.WithTimeoutCause(
 		ctx, core.GetGithubTimeout(),
 		fmt.Errorf("creating PR too slow, increase github.timeout"),

core/repo.go

@@ -175,6 +175,18 @@ func (r *Repo) Checkout(branch Branch) error {
 	return cmd.Run()
 }
 
+func (r *Repo) CheckoutRef(ref *plumbing.Reference) error {
+	checkout := ref.Hash().String()
+	if ref.Name().IsBranch() {
+		checkout = ref.Name().Short()
+	}
+	cmd := r.GitExec(context.Background(), "checkout %s", checkout)
+	cmd.Stderr = nil
+	cmd.Stdout = nil
+	cmd.Stdin = os.Stdin
+	return cmd.Run()
+}
+
 func (r *Repo) GitExec(ctx context.Context, format string, args ...any) *exec.Cmd {
 	cmd := exec.CommandContext(ctx, "bash", "-c", "git "+fmt.Sprintf(format, args...))
 	cmd.Dir = r.Path()
@@ -215,12 +227,12 @@ func (r *Repo) TryRebaseCurrentBranchSilently(ctx context.Context, branch Branch
 	return false
 }
 
-func (r *Repo) TryRebaseOntoSilently(ctx context.Context, first plumbing.Hash, last plumbing.Hash, onto Branch, interactive bool) bool {
+func (r *Repo) TryRebaseOntoSilently(ctx context.Context, first plumbing.Hash, onto Branch, interactive bool) bool {
 	interactiveString := ""
 	if interactive {
 		interactiveString = "--interactive"
 	}
-	cmd := r.GitExec(ctx, "rebase %s --onto %s/%s %s^ %s", interactiveString, GetRemoteName(), onto.RemoteName(), first.String(), last.String())
+	cmd := r.GitExec(ctx, "rebase %s --onto %s/%s %s^", interactiveString, GetRemoteName(), onto.RemoteName(), first.String())
 	err := cmd.Run()
 	if err == nil {
 		return true
@@ -378,3 +390,8 @@ func (r *Repo) DeleteRemoteBranch(ctx context.Context, branch Branch) error {
 	cmd := r.GitExec(ctx, "push %s :%s", GetRemoteName(), branch.RemoteName())
 	return cmd.Run()
 }
+
+func (r *Repo) DetachHead(ctx context.Context) error {
+	cmd := r.GitExec(ctx, "checkout --detach HEAD")
+	return cmd.Run()
+}