fix: restore the original branch after promote

README.md

@@ -83,7 +83,7 @@ promptctl push -server prompts.internal:8443
 
 `promote` models dev → staging → prod as git branches: it copies a validated
 prompt from one branch onto another and commits it — a deliberate, recorded
-promotion instead of a copy-paste.
+promotion instead of a copy-paste. You stay on the branch you ran it from.
 
 ```mermaid
 flowchart LR

cmd/promptctl/main.go

@@ -143,7 +143,7 @@ func logCmd(args []string) {
 // promote brings one prompt from the `from` branch onto the `to` branch and
 // commits it there — the dev → staging → prod version promotion. A no-op (the
 // prompt already matches on `to`) reports "already up to date" instead of failing
-// on an empty commit.
+// on an empty commit. The branch (or commit) checked out before is restored after.
 // ponytail: assumes both branches exist and the tree is clean; go-git errors surface as-is.
 func promote(args []string) {
 	if len(args) != 3 {
@@ -165,22 +165,41 @@ func promote(args []string) {
 	}
 
 	wt := worktree(r)
+	head, err := r.Head()
+	if err != nil {
+		log.Fatal(err)
+	}
 	if err := wt.Checkout(&git.CheckoutOptions{Branch: plumbing.NewBranchReferenceName(to)}); err != nil {
 		log.Fatalf("checkout %s: %v", to, err)
 	}
-	if err := os.WriteFile(filepath.FromSlash(path), []byte(content), 0o644); err != nil {
-		log.Fatal(err)
+	h, err := commitFile(r, wt, path, content, fmt.Sprintf("promote %s: %s -> %s", path, from, to))
+
+	// Switch back to where the user was (their branch, or a detached commit),
+	// whether or not the commit landed.
+	back := &git.CheckoutOptions{Branch: head.Name()}
+	if !head.Name().IsBranch() {
+		back = &git.CheckoutOptions{Hash: head.Hash()}
 	}
-	if _, err := wt.Add(path); err != nil {
-		log.Fatal(err)
+	if berr := wt.Checkout(back); berr != nil {
+		log.Fatalf("checkout %s (to switch back from %s): %v", head.Name().Short(), to, berr)
 	}
-	h, err := wt.Commit(fmt.Sprintf("promote %s: %s -> %s", path, from, to), &git.CommitOptions{Author: author(r)})
 	if err != nil {
 		log.Fatal(err)
 	}
 	fmt.Printf("promoted %s onto %s (%s)\n", path, to, h.String()[:12])
 }
 
+// commitFile writes content to path in the checked-out worktree and commits it.
+func commitFile(r *git.Repository, wt *git.Worktree, path, content, msg string) (plumbing.Hash, error) {
+	if err := os.WriteFile(filepath.FromSlash(path), []byte(content), 0o644); err != nil {
+		return plumbing.ZeroHash, err
+	}
+	if _, err := wt.Add(path); err != nil {
+		return plumbing.ZeroHash, err
+	}
+	return wt.Commit(msg, &git.CommitOptions{Author: author(r)})
+}
+
 // pushCmd validates, pushes to the git remote, and — if -server is given —
 // publishes every prompt to that live server so subscribers are notified.
 // Publishing is idempotent server-side, so only actually-changed prompts notify.

cmd/promptctl/promote_test.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/object"
+)
+
+func TestPromoteRestoresBranch(t *testing.T) {
+	const devContent = "Hello {name}, welcome to {org}.\n"
+	dir := t.TempDir()
+	t.Chdir(dir)
+	r, err := git.PlainInit(dir, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	wt, _ := r.Worktree()
+	commit := func(content, msg string) {
+		t.Helper()
+		if err := os.MkdirAll("acme", 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile("acme/a.prompt", []byte(content), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := wt.Add("acme/a.prompt"); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := wt.Commit(msg, &git.CommitOptions{Author: &object.Signature{Name: "t", Email: "t@t"}}); err != nil {
+			t.Fatal(err)
+		}
+	}
+	commit("Hello {name}.\n", "init")
+	head, _ := r.Head()
+	for _, b := range []string{"staging", "dev"} {
+		if err := r.Storer.SetReference(plumbing.NewHashReference(plumbing.NewBranchReferenceName(b), head.Hash())); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := wt.Checkout(&git.CheckoutOptions{Branch: plumbing.NewBranchReferenceName("dev")}); err != nil {
+		t.Fatal(err)
+	}
+	commit(devContent, "dev edit")
+
+	promote([]string{"acme/a.prompt", "dev", "staging"})
+
+	if h, _ := r.Head(); h.Name().Short() != "dev" {
+		t.Errorf("after promote HEAD is %s, want dev (the branch it started on)", h.Name().Short())
+	}
+	if got := diskContent("acme/a.prompt"); got != devContent {
+		t.Errorf("working tree has %q, want dev's content", got)
+	}
+	if got := blobContent(treeAt(r, "staging"), "acme/a.prompt"); got != devContent {
+		t.Errorf("staging has %q, want the promoted content", got)
+	}
+}