Auto-import from git on empty DB (bd-189)

- Add checkAndAutoImport() that detects empty DB with issues in git
- Automatically imports from git HEAD:.beads/issues.jsonl
- Integrated into list, ready, and stats commands
- Zero cognitive load for agents in fresh clones
- Makes JSONL truly the source of truth
- DB becomes ephemeral cache that auto-rebuilds

Also:
- Update AGENTS.md onboarding section with import instructions
- Merge PR #98 (enhanced .gitignore)

Amp-Thread-ID: https://ampcode.com/threads/T-ffcb5e95-e5a0-486b-a0ae-ce8bd861ab9d
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/autoimport.go

@@ -0,0 +1,171 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/steveyegge/beads/internal/storage"
+	"github.com/steveyegge/beads/internal/types"
+)
+
+// checkAndAutoImport checks if the database is empty but git has issues.
+// If so, it automatically imports them and returns true.
+// Returns false if no import was needed or if import failed.
+func checkAndAutoImport(ctx context.Context, store storage.Storage) bool {
+	// Don't auto-import if auto-import is explicitly disabled
+	if noAutoImport {
+		return false
+	}
+
+	// Check if database has any issues
+	stats, err := store.GetStatistics(ctx)
+	if err != nil || stats.TotalIssues > 0 {
+		// Either error checking or DB has issues - don't auto-import
+		return false
+	}
+
+	// Database is empty - check if git has issues
+	issueCount, jsonlPath := checkGitForIssues()
+	if issueCount == 0 {
+		// No issues in git either
+		return false
+	}
+
+	// Found issues in git! Auto-import them
+	if !jsonOutput {
+		fmt.Fprintf(os.Stderr, "Found 0 issues in database but %d in git. Importing...\n", issueCount)
+	}
+
+	// Import from git
+	if err := importFromGit(ctx, store, jsonlPath); err != nil {
+		if !jsonOutput {
+			fmt.Fprintf(os.Stderr, "Warning: auto-import failed: %v\n", err)
+			fmt.Fprintf(os.Stderr, "Try manually: git show HEAD:%s | bd import -i /dev/stdin\n", jsonlPath)
+		}
+		return false
+	}
+
+	if !jsonOutput {
+		fmt.Fprintf(os.Stderr, "Successfully imported %d issues from git.\n\n", issueCount)
+	}
+
+	return true
+}
+
+// checkGitForIssues checks if git has issues in HEAD:.beads/issues.jsonl
+// Returns (issue_count, relative_jsonl_path)
+func checkGitForIssues() (int, string) {
+	// Try to find .beads directory
+	beadsDir := findBeadsDir()
+	if beadsDir == "" {
+		return 0, ""
+	}
+
+	// Construct relative path to issues.jsonl from git root
+	gitRoot := findGitRoot()
+	if gitRoot == "" {
+		return 0, ""
+	}
+
+	relPath, err := filepath.Rel(gitRoot, filepath.Join(beadsDir, "issues.jsonl"))
+	if err != nil {
+		return 0, ""
+	}
+
+	// Check if git has this file with content
+	cmd := exec.Command("git", "show", fmt.Sprintf("HEAD:%s", relPath))
+	output, err := cmd.Output()
+	if err != nil {
+		// File doesn't exist in git or other error
+		return 0, ""
+	}
+
+	// Count lines (rough estimate of issue count)
+	lines := bytes.Count(output, []byte("\n"))
+	if lines == 0 {
+		return 0, ""
+	}
+
+	return lines, relPath
+}
+
+// findBeadsDir finds the .beads directory in current or parent directories
+func findBeadsDir() string {
+	dir, err := os.Getwd()
+	if err != nil {
+		return ""
+	}
+
+	for {
+		beadsDir := filepath.Join(dir, ".beads")
+		if info, err := os.Stat(beadsDir); err == nil && info.IsDir() {
+			return beadsDir
+		}
+
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			// Reached root
+			break
+		}
+		dir = parent
+	}
+
+	return ""
+}
+
+// findGitRoot finds the git repository root
+func findGitRoot() string {
+	cmd := exec.Command("git", "rev-parse", "--show-toplevel")
+	output, err := cmd.Output()
+	if err != nil {
+		return ""
+	}
+	return string(bytes.TrimSpace(output))
+}
+
+// importFromGit imports issues from git HEAD
+func importFromGit(ctx context.Context, store storage.Storage, jsonlPath string) error {
+	// Get content from git
+	cmd := exec.Command("git", "show", fmt.Sprintf("HEAD:%s", jsonlPath))
+	jsonlData, err := cmd.Output()
+	if err != nil {
+		return fmt.Errorf("failed to read from git: %w", err)
+	}
+
+	// Parse JSONL data
+	scanner := bufio.NewScanner(bytes.NewReader(jsonlData))
+	var issues []*types.Issue
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" {
+			continue
+		}
+
+		var issue types.Issue
+		if err := json.Unmarshal([]byte(line), &issue); err != nil {
+			return fmt.Errorf("failed to parse issue: %w", err)
+		}
+		issues = append(issues, &issue)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return fmt.Errorf("failed to scan JSONL: %w", err)
+	}
+
+	// Use existing import logic with auto-resolve collisions
+	opts := ImportOptions{
+		ResolveCollisions: true,
+		DryRun:            false,
+		SkipUpdate:        false,
+	}
+
+	_, err = importIssuesCore(ctx, dbPath, store, issues, opts)
+	return err
+}