test: add git helper and guard annotations

cmd/bd/git_test_helpers.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"github.com/steveyegge/beads/internal/git"
+)
+
+// runInDir changes into dir, resets git caches before/after, and executes fn.
+// It ensures tests that mutate git repositories don't leak state across cases.
+func runInDir(t *testing.T, dir string, fn func()) {
+	t.Helper()
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("failed to get working directory: %v", err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("failed to change to temp directory: %v", err)
+	}
+	git.ResetCaches()
+	defer func() {
+		if err := os.Chdir(origDir); err != nil {
+			t.Fatalf("failed to restore working directory: %v", err)
+		}
+		git.ResetCaches()
+	}()
+	fn()
+}