fix(daemon): check sync-branch upstream for jj/jujutsu compatibility

When sync-branch is configured, check that branch's upstream instead of
current HEAD's upstream. This fixes --auto-push with jj/jujutsu which
always operates in detached HEAD mode.

Adds gitBranchHasUpstream(branch) to check specific branch's upstream
tracking, independent of current HEAD state.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/sync_git_test.go

@@ -1,6 +1,9 @@
 package main
 
 import (
+	"os"
+	"os/exec"
+	"path/filepath"
 	"testing"
 )
 
@@ -98,3 +101,129 @@ func TestParseGitStatusForBeadsChanges(t *testing.T) {
 		})
 	}
 }
+
+// TestGitBranchHasUpstream tests the gitBranchHasUpstream function
+// which checks if a specific branch (not current HEAD) has upstream configured.
+// This is critical for jj/jujutsu compatibility where HEAD is always detached
+// but the sync-branch may have proper upstream tracking.
+func TestGitBranchHasUpstream(t *testing.T) {
+	// Create temp directory for test repos
+	tmpDir, err := os.MkdirTemp("", "beads-upstream-test-*")
+	if err != nil {
+		t.Fatalf("Failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// Create a bare "remote" repo
+	remoteDir := filepath.Join(tmpDir, "remote.git")
+	if err := exec.Command("git", "init", "--bare", remoteDir).Run(); err != nil {
+		t.Fatalf("Failed to create bare repo: %v", err)
+	}
+
+	// Create local repo
+	localDir := filepath.Join(tmpDir, "local")
+	if err := os.MkdirAll(localDir, 0755); err != nil {
+		t.Fatalf("Failed to create local dir: %v", err)
+	}
+
+	// Initialize and configure local repo
+	cmds := [][]string{
+		{"git", "init", "-b", "main"},
+		{"git", "config", "user.email", "test@test.com"},
+		{"git", "config", "user.name", "Test"},
+		{"git", "remote", "add", "origin", remoteDir},
+	}
+	for _, args := range cmds {
+		cmd := exec.Command(args[0], args[1:]...)
+		cmd.Dir = localDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("Failed to run %v: %v\n%s", args, err, out)
+		}
+	}
+
+	// Create initial commit on main
+	testFile := filepath.Join(localDir, "test.txt")
+	if err := os.WriteFile(testFile, []byte("test"), 0644); err != nil {
+		t.Fatalf("Failed to create test file: %v", err)
+	}
+	cmds = [][]string{
+		{"git", "add", "test.txt"},
+		{"git", "commit", "-m", "initial"},
+		{"git", "push", "-u", "origin", "main"},
+	}
+	for _, args := range cmds {
+		cmd := exec.Command(args[0], args[1:]...)
+		cmd.Dir = localDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("Failed to run %v: %v\n%s", args, err, out)
+		}
+	}
+
+	// Create beads-sync branch with upstream
+	cmds = [][]string{
+		{"git", "checkout", "-b", "beads-sync"},
+		{"git", "push", "-u", "origin", "beads-sync"},
+	}
+	for _, args := range cmds {
+		cmd := exec.Command(args[0], args[1:]...)
+		cmd.Dir = localDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("Failed to run %v: %v\n%s", args, err, out)
+		}
+	}
+
+	// Save current dir and change to local repo
+	origDir, _ := os.Getwd()
+	if err := os.Chdir(localDir); err != nil {
+		t.Fatalf("Failed to chdir: %v", err)
+	}
+	defer os.Chdir(origDir)
+
+	// Test 1: beads-sync branch should have upstream
+	t.Run("branch with upstream returns true", func(t *testing.T) {
+		if !gitBranchHasUpstream("beads-sync") {
+			t.Error("gitBranchHasUpstream('beads-sync') = false, want true")
+		}
+	})
+
+	// Test 2: non-existent branch should return false
+	t.Run("non-existent branch returns false", func(t *testing.T) {
+		if gitBranchHasUpstream("no-such-branch") {
+			t.Error("gitBranchHasUpstream('no-such-branch') = true, want false")
+		}
+	})
+
+	// Test 3: Simulate jj detached HEAD - beads-sync should still work
+	t.Run("works with detached HEAD (jj scenario)", func(t *testing.T) {
+		// Detach HEAD (simulating jj's behavior)
+		cmd := exec.Command("git", "checkout", "--detach", "HEAD")
+		cmd.Dir = localDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("Failed to detach HEAD: %v\n%s", err, out)
+		}
+
+		// gitHasUpstream() should fail (detached HEAD)
+		if gitHasUpstream() {
+			t.Error("gitHasUpstream() = true with detached HEAD, want false")
+		}
+
+		// But gitBranchHasUpstream("beads-sync") should still work
+		if !gitBranchHasUpstream("beads-sync") {
+			t.Error("gitBranchHasUpstream('beads-sync') = false with detached HEAD, want true")
+		}
+	})
+
+	// Test 4: branch without upstream should return false
+	t.Run("branch without upstream returns false", func(t *testing.T) {
+		// Create a local-only branch (no upstream)
+		cmd := exec.Command("git", "checkout", "-b", "local-only")
+		cmd.Dir = localDir
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("Failed to create local branch: %v\n%s", err, out)
+		}
+
+		if gitBranchHasUpstream("local-only") {
+			t.Error("gitBranchHasUpstream('local-only') = true, want false (no upstream)")
+		}
+	})
+}