split main.go into modules, add --version flag

config.go

@@ -0,0 +1,219 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+
+	lua "github.com/yuin/gopher-lua"
+)
+
+const (
+	configFileName = "config.lua"
+	filesDirName   = "files"
+)
+
+type packageConfig struct {
+	targets         map[string]string
+	disabled        map[string]bool
+	ignore          []string
+	compiledIgnores []*regexp.Regexp
+}
+
+var errTargetDisabled = errors.New("target disabled for this platform")
+
+func loadConfig(path string) (*packageConfig, error) {
+	L := lua.NewState()
+	defer L.Close()
+	L.OpenLibs()
+
+	if err := L.DoFile(path); err != nil {
+		return nil, err
+	}
+	if L.GetTop() == 0 {
+		return nil, errors.New("config.lua must return a table")
+	}
+
+	value := L.Get(-1)
+	tbl, ok := value.(*lua.LTable)
+	if !ok {
+		return nil, errors.New("config.lua must return a table")
+	}
+
+	targetVal := tbl.RawGetString("target")
+	targetTbl, ok := targetVal.(*lua.LTable)
+	if !ok {
+		return nil, errors.New("config.target must be a table")
+	}
+
+	targets := make(map[string]string)
+	disabled := make(map[string]bool)
+	targetTbl.ForEach(func(k, v lua.LValue) {
+		ks, ok := k.(lua.LString)
+		if !ok {
+			return
+		}
+
+		if v == lua.LNil || v == lua.LFalse {
+			disabled[string(ks)] = true
+			return
+		}
+
+		vs, ok := v.(lua.LString)
+		if !ok {
+			return
+		}
+
+		targets[string(ks)] = expandHome(string(vs))
+	})
+
+	if len(targets) == 0 && len(disabled) == 0 {
+		return nil, errors.New("config.target is empty")
+	}
+
+	ignore, err := parseIgnore(tbl)
+	if err != nil {
+		return nil, err
+	}
+	compiledIgnores, err := compileIgnorePatterns(ignore)
+	if err != nil {
+		return nil, err
+	}
+
+	return &packageConfig{targets: targets, disabled: disabled, ignore: ignore, compiledIgnores: compiledIgnores}, nil
+}
+
+func selectTarget(cfg *packageConfig) (string, error) {
+	osKey := runtime.GOOS
+	if osKey == "darwin" {
+		osKey = "macos"
+	}
+	if cfg.disabled[osKey] {
+		return "", errTargetDisabled
+	}
+	if target, ok := cfg.targets[osKey]; ok {
+		return expandHome(target), nil
+	}
+	if target, ok := cfg.targets["default"]; ok {
+		return expandHome(target), nil
+	}
+	return "", fmt.Errorf("missing target for %s and default", osKey)
+}
+
+func parseIgnore(cfgTbl *lua.LTable) ([]string, error) {
+	ignoreVal := cfgTbl.RawGetString("ignore")
+	if ignoreVal == lua.LNil {
+		return nil, nil
+	}
+
+	ignoreTbl, ok := ignoreVal.(*lua.LTable)
+	if !ok {
+		return nil, errors.New("config.ignore must be an array of strings")
+	}
+
+	ignore := make([]string, 0, ignoreTbl.Len())
+	var parseErr error
+	ignoreTbl.ForEach(func(k, v lua.LValue) {
+		if parseErr != nil {
+			return
+		}
+
+		if _, ok := k.(lua.LNumber); !ok {
+			parseErr = errors.New("config.ignore must be an array of strings")
+			return
+		}
+
+		s, ok := v.(lua.LString)
+		if !ok {
+			parseErr = errors.New("config.ignore must contain only strings")
+			return
+		}
+
+		pattern := strings.TrimSpace(string(s))
+		if pattern == "" {
+			parseErr = errors.New("config.ignore cannot contain empty patterns")
+			return
+		}
+
+		ignore = append(ignore, pattern)
+	})
+	if parseErr != nil {
+		return nil, parseErr
+	}
+	return ignore, nil
+}
+
+func compileIgnorePatterns(patterns []string) ([]*regexp.Regexp, error) {
+	compiled := make([]*regexp.Regexp, 0, len(patterns))
+	for _, pattern := range patterns {
+		re, err := globToRegexp(pattern)
+		if err != nil {
+			return nil, fmt.Errorf("invalid ignore pattern %q: %w", pattern, err)
+		}
+		compiled = append(compiled, re)
+	}
+	return compiled, nil
+}
+
+func globToRegexp(pattern string) (*regexp.Regexp, error) {
+	pattern = strings.ReplaceAll(pattern, "\\", "/")
+	pattern = strings.TrimPrefix(pattern, "./")
+	if strings.HasPrefix(pattern, "/") {
+		pattern = strings.TrimPrefix(pattern, "/")
+	}
+
+	var b strings.Builder
+	b.WriteString("^")
+	for i := 0; i < len(pattern); {
+		if i+1 < len(pattern) && pattern[i] == '*' && pattern[i+1] == '*' {
+			b.WriteString(".*")
+			i += 2
+			continue
+		}
+
+		ch := pattern[i]
+		switch ch {
+		case '*':
+			b.WriteString("[^/]*")
+		case '?':
+			b.WriteString("[^/]")
+		default:
+			b.WriteString(regexp.QuoteMeta(string(ch)))
+		}
+		i++
+	}
+	b.WriteString("$")
+
+	return regexp.Compile(b.String())
+}
+
+func shouldIgnorePath(rel string, cfg *packageConfig) bool {
+	if cfg == nil || len(cfg.compiledIgnores) == 0 {
+		return false
+	}
+
+	normalized := path.Clean(filepath.ToSlash(rel))
+	for _, re := range cfg.compiledIgnores {
+		if re.MatchString(normalized) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func writeConfig(path, targetRoot string) error {
+	osKey := "linux"
+	if runtime.GOOS == "darwin" {
+		osKey = "macos"
+	}
+
+	prettyTarget := compressHome(targetRoot)
+	content := fmt.Sprintf("---@class SigilConfig\n---@field target table<string, string|boolean>\n---@field ignore? string[]\n\n---@type SigilConfig\nlocal config = {\n\ttarget = {\n\t\t%s = %q,\n\t\tdefault = %q,\n\t},\n\tignore = {\n\t\t-- \"**/.DS_Store\",\n\t\t-- \"**/*.tmp\",\n\t\t-- \"cache/**\",\n\t},\n}\n\nreturn config\n", osKey, prettyTarget, prettyTarget)
+	return os.WriteFile(path, []byte(content), 0o644)
+}

main.go

@@ -1,34 +1,14 @@
 package main
 
 import (
-	"bufio"
 	"errors"
 	"fmt"
-	"io"
-	"io/fs"
 	"os"
-	"path"
 	"path/filepath"
-	"regexp"
-	"runtime"
 	"strings"
-
-	lua "github.com/yuin/gopher-lua"
 )
 
-const (
+const version = "0.1.0"
-	configFileName = "config.lua"
-	filesDirName   = "files"
-)
-
-type packageConfig struct {
-	targets         map[string]string
-	disabled        map[string]bool
-	ignore          []string
-	compiledIgnores []*regexp.Regexp
-}
-
-var errTargetDisabled = errors.New("target disabled for this platform")
 
 func main() {
 	if len(os.Args) < 2 {
@@ -38,6 +18,11 @@ func main() {
 
 	args := os.Args[1:]
 
+	if args[0] == "-v" || args[0] == "--version" {
+		fmt.Println("sigil", version)
+		os.Exit(0)
+	}
+
 	var err error
 	switch args[0] {
 	case "apply":
@@ -73,142 +58,6 @@ func usage() {
 	fmt.Println("  sigil status")
 }
 
-type packageFlags struct {
-	dryRun bool
-}
-
-func parsePackageFlags(args []string) (packageFlags, string, error) {
-	flags := packageFlags{}
-	var pkg string
-	for _, arg := range args {
-		if arg == "--dry-run" {
-			flags.dryRun = true
-			continue
-		}
-		if strings.HasPrefix(arg, "-") {
-			return flags, "", fmt.Errorf("unknown flag %q", arg)
-		}
-		if pkg != "" {
-			return flags, "", errors.New("too many arguments")
-		}
-		pkg = arg
-	}
-	if pkg == "" {
-		return flags, "", errors.New("missing package")
-	}
-	return flags, pkg, nil
-}
-
-func splitPackageSpec(spec string) (string, string, error) {
-	if spec == "" {
-		return "", "", errors.New("missing package")
-	}
-
-	parts := strings.SplitN(spec, ":", 2)
-	pkg := parts[0]
-	rel := ""
-	if len(parts) == 2 {
-		rel = parts[1]
-	}
-
-	pkg = strings.Trim(pkg, "/")
-	rel = strings.TrimPrefix(rel, "/")
-
-	if pkg == "" {
-		return "", "", errors.New("invalid package")
-	}
-
-	return pkg, rel, nil
-}
-
-func resolvePackageSpec(spec string) (string, string, error) {
-	repo, err := repoPath()
-	if err != nil {
-		return "", "", err
-	}
-
-	repoAbs, err := filepath.Abs(repo)
-	if err != nil {
-		return "", "", err
-	}
-
-	spec = expandHome(spec)
-	if filepath.IsAbs(spec) {
-		return resolvePathSpec(spec, repoAbs)
-	}
-
-	if strings.Contains(spec, string(os.PathSeparator)) {
-		return resolvePathSpec(spec, repoAbs)
-	}
-
-	clean := filepath.Clean(spec)
-	if strings.HasPrefix(clean, ".") || strings.HasPrefix(clean, string(os.PathSeparator)) {
-		return resolvePathSpec(clean, repoAbs)
-	}
-
-	return splitPackageSpec(spec)
-}
-
-func resolvePathSpec(pathSpec, repoAbs string) (string, string, error) {
-	absPath, err := filepath.Abs(pathSpec)
-	if err != nil {
-		return "", "", err
-	}
-
-	if strings.HasPrefix(absPath, repoAbs+string(os.PathSeparator)) || absPath == repoAbs {
-		rel, err := filepath.Rel(repoAbs, absPath)
-		if err != nil {
-			return "", "", err
-		}
-		parts := strings.Split(rel, string(os.PathSeparator))
-		if len(parts) >= 1 {
-			pkg := parts[0]
-			if len(parts) >= 2 && parts[1] == filesDirName {
-				relPath := filepath.Join(parts[2:]...)
-				return pkg, relPath, nil
-			}
-			return pkg, filepath.Join(parts[1:]...), nil
-		}
-	}
-
-	entries, err := os.ReadDir(repoAbs)
-	if err != nil {
-		return "", "", err
-	}
-
-	for _, entry := range entries {
-		if !entry.IsDir() || strings.HasPrefix(entry.Name(), ".") {
-			continue
-		}
-		pkgDir := filepath.Join(repoAbs, entry.Name())
-		configPath := filepath.Join(pkgDir, configFileName)
-		cfg, err := loadConfig(configPath)
-		if err != nil {
-			continue
-		}
-		targetRoot, err := selectTarget(cfg)
-		if err != nil {
-			if errors.Is(err, errTargetDisabled) {
-				continue
-			}
-			continue
-		}
-		absTarget, err := filepath.Abs(expandHome(targetRoot))
-		if err != nil {
-			continue
-		}
-		if strings.HasPrefix(absPath, absTarget+string(os.PathSeparator)) || absPath == absTarget {
-			rel, err := filepath.Rel(absTarget, absPath)
-			if err != nil {
-				return "", "", err
-			}
-			return entry.Name(), rel, nil
-		}
-	}
-
-	return "", "", fmt.Errorf("could not resolve %s to a package", pathSpec)
-}
-
 func applyCmd(args []string) error {
 	prune := false
 	for _, arg := range args {
@@ -332,7 +181,6 @@ func addCmd(args []string) error {
 		defaultPkg = filepath.Base(absPath)
 	}
 
-	reader := bufio.NewReader(os.Stdin)
 	var pkgName string
 
 	matchedPkg, err := findPackageByTarget(repo, defaultTarget)
@@ -350,7 +198,7 @@ func addCmd(args []string) error {
 	}
 
 	if pkgName == "" {
-		pkgName = promptWithDefault(reader, "Package name", defaultPkg)
+		pkgName = promptWithDefault("Package name", defaultPkg)
 		if pkgName == "" {
 			return errors.New("package name cannot be empty")
 		}
@@ -358,7 +206,7 @@ func addCmd(args []string) error {
 
 	targetRootInput := defaultTarget
 	if pkgName != matchedPkg || matchedPkg == "" {
-		targetRootInput = promptWithDefault(reader, "Target path", defaultTarget)
+		targetRootInput = promptWithDefault("Target path", defaultTarget)
 	}
 	targetRoot, err := filepath.Abs(expandHome(targetRootInput))
 	if err != nil {
@@ -544,144 +392,6 @@ func removeCmd(args []string) error {
 	return nil
 }
 
-func applyPackage(filesDir, targetRoot string, cfg *packageConfig) error {
-	if err := ensureDir(targetRoot); err != nil {
-		return err
-	}
-
-	return filepath.WalkDir(filesDir, func(path string, entry fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-		if path == filesDir {
-			return nil
-		}
-
-		rel, err := filepath.Rel(filesDir, path)
-		if err != nil {
-			return err
-		}
-
-		if shouldIgnorePath(rel, cfg) {
-			if entry.IsDir() {
-				return filepath.SkipDir
-			}
-			return nil
-		}
-
-		targetPath := filepath.Join(targetRoot, rel)
-
-		if entry.IsDir() {
-			return ensureDir(targetPath)
-		}
-
-		srcAbs, err := filepath.Abs(path)
-		if err != nil {
-			return err
-		}
-		return linkFile(srcAbs, targetPath)
-	})
-}
-
-func linkFile(src, dst string) error {
-	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
-		return err
-	}
-
-	if info, err := os.Lstat(dst); err == nil {
-		if info.Mode()&os.ModeSymlink != 0 {
-			current, err := os.Readlink(dst)
-			if err != nil {
-				return err
-			}
-			if current == src {
-				return nil
-			}
-			return fmt.Errorf("conflict at %s (points to %s)", dst, current)
-		}
-		return fmt.Errorf("conflict at %s (exists and is not a symlink)", dst)
-	} else if !errors.Is(err, os.ErrNotExist) {
-		return err
-	}
-
-	return os.Symlink(src, dst)
-}
-
-func ensureDir(path string) error {
-	info, err := os.Lstat(path)
-	if err == nil {
-		if info.IsDir() {
-			return nil
-		}
-		return fmt.Errorf("%s exists and is not a directory", path)
-	}
-	if !errors.Is(err, os.ErrNotExist) {
-		return err
-	}
-	return os.MkdirAll(path, 0o755)
-}
-
-func loadConfig(path string) (*packageConfig, error) {
-	L := lua.NewState()
-	defer L.Close()
-	L.OpenLibs()
-
-	if err := L.DoFile(path); err != nil {
-		return nil, err
-	}
-	if L.GetTop() == 0 {
-		return nil, errors.New("config.lua must return a table")
-	}
-
-	value := L.Get(-1)
-	tbl, ok := value.(*lua.LTable)
-	if !ok {
-		return nil, errors.New("config.lua must return a table")
-	}
-
-	targetVal := tbl.RawGetString("target")
-	targetTbl, ok := targetVal.(*lua.LTable)
-	if !ok {
-		return nil, errors.New("config.target must be a table")
-	}
-
-	targets := make(map[string]string)
-	disabled := make(map[string]bool)
-	targetTbl.ForEach(func(k, v lua.LValue) {
-		ks, ok := k.(lua.LString)
-		if !ok {
-			return
-		}
-
-		if v == lua.LNil || v == lua.LFalse {
-			disabled[string(ks)] = true
-			return
-		}
-
-		vs, ok := v.(lua.LString)
-		if !ok {
-			return
-		}
-
-		targets[string(ks)] = expandHome(string(vs))
-	})
-
-	if len(targets) == 0 && len(disabled) == 0 {
-		return nil, errors.New("config.target is empty")
-	}
-
-	ignore, err := parseIgnore(tbl)
-	if err != nil {
-		return nil, err
-	}
-	compiledIgnores, err := compileIgnorePatterns(ignore)
-	if err != nil {
-		return nil, err
-	}
-
-	return &packageConfig{targets: targets, disabled: disabled, ignore: ignore, compiledIgnores: compiledIgnores}, nil
-}
-
 func statusCmd() error {
 	repo, err := repoPath()
 	if err != nil {
@@ -731,605 +441,3 @@ func statusCmd() error {
 
 	return nil
 }
-
-func selectTarget(cfg *packageConfig) (string, error) {
-	osKey := runtime.GOOS
-	if osKey == "darwin" {
-		osKey = "macos"
-	}
-	if cfg.disabled[osKey] {
-		return "", errTargetDisabled
-	}
-	if target, ok := cfg.targets[osKey]; ok {
-		return expandHome(target), nil
-	}
-	if target, ok := cfg.targets["default"]; ok {
-		return expandHome(target), nil
-	}
-	return "", fmt.Errorf("missing target for %s and default", osKey)
-}
-
-func parseIgnore(cfgTbl *lua.LTable) ([]string, error) {
-	ignoreVal := cfgTbl.RawGetString("ignore")
-	if ignoreVal == lua.LNil {
-		return nil, nil
-	}
-
-	ignoreTbl, ok := ignoreVal.(*lua.LTable)
-	if !ok {
-		return nil, errors.New("config.ignore must be an array of strings")
-	}
-
-	ignore := make([]string, 0, ignoreTbl.Len())
-	var parseErr error
-	ignoreTbl.ForEach(func(k, v lua.LValue) {
-		if parseErr != nil {
-			return
-		}
-
-		if _, ok := k.(lua.LNumber); !ok {
-			parseErr = errors.New("config.ignore must be an array of strings")
-			return
-		}
-
-		s, ok := v.(lua.LString)
-		if !ok {
-			parseErr = errors.New("config.ignore must contain only strings")
-			return
-		}
-
-		pattern := strings.TrimSpace(string(s))
-		if pattern == "" {
-			parseErr = errors.New("config.ignore cannot contain empty patterns")
-			return
-		}
-
-		ignore = append(ignore, pattern)
-	})
-	if parseErr != nil {
-		return nil, parseErr
-	}
-	return ignore, nil
-}
-
-func compileIgnorePatterns(patterns []string) ([]*regexp.Regexp, error) {
-	compiled := make([]*regexp.Regexp, 0, len(patterns))
-	for _, pattern := range patterns {
-		re, err := globToRegexp(pattern)
-		if err != nil {
-			return nil, fmt.Errorf("invalid ignore pattern %q: %w", pattern, err)
-		}
-		compiled = append(compiled, re)
-	}
-	return compiled, nil
-}
-
-func globToRegexp(pattern string) (*regexp.Regexp, error) {
-	pattern = strings.ReplaceAll(pattern, "\\", "/")
-	pattern = strings.TrimPrefix(pattern, "./")
-	if strings.HasPrefix(pattern, "/") {
-		pattern = strings.TrimPrefix(pattern, "/")
-	}
-
-	var b strings.Builder
-	b.WriteString("^")
-	for i := 0; i < len(pattern); {
-		if i+1 < len(pattern) && pattern[i] == '*' && pattern[i+1] == '*' {
-			b.WriteString(".*")
-			i += 2
-			continue
-		}
-
-		ch := pattern[i]
-		switch ch {
-		case '*':
-			b.WriteString("[^/]*")
-		case '?':
-			b.WriteString("[^/]")
-		default:
-			b.WriteString(regexp.QuoteMeta(string(ch)))
-		}
-		i++
-	}
-	b.WriteString("$")
-
-	return regexp.Compile(b.String())
-}
-
-func shouldIgnorePath(rel string, cfg *packageConfig) bool {
-	if cfg == nil || len(cfg.compiledIgnores) == 0 {
-		return false
-	}
-
-	normalized := path.Clean(filepath.ToSlash(rel))
-	for _, re := range cfg.compiledIgnores {
-		if re.MatchString(normalized) {
-			return true
-		}
-	}
-
-	return false
-}
-
-func repoPath() (string, error) {
-	if override := os.Getenv("SIGIL_REPO"); override != "" {
-		return filepath.Abs(expandHome(override))
-	}
-	return filepath.Abs(expandHome("~/.dotfiles"))
-}
-
-func expandHome(path string) string {
-	if path == "~" {
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return path
-		}
-		return home
-	}
-	if strings.HasPrefix(path, "~/") {
-		home, err := os.UserHomeDir()
-		if err != nil {
-			return path
-		}
-		return filepath.Join(home, path[2:])
-	}
-	return path
-}
-
-func compressHome(path string) string {
-	home, err := os.UserHomeDir()
-	if err != nil {
-		return path
-	}
-	clean := filepath.Clean(path)
-	homeClean := filepath.Clean(home)
-	if clean == homeClean {
-		return "~"
-	}
-	if strings.HasPrefix(clean, homeClean+string(os.PathSeparator)) {
-		rel := strings.TrimPrefix(clean, homeClean+string(os.PathSeparator))
-		return filepath.Join("~", rel)
-	}
-	return path
-}
-
-func writeConfig(path, targetRoot string) error {
-	osKey := "linux"
-	if runtime.GOOS == "darwin" {
-		osKey = "macos"
-	}
-
-	prettyTarget := compressHome(targetRoot)
-	content := fmt.Sprintf("---@class SigilConfig\n---@field target table<string, string|boolean>\n---@field ignore? string[]\n\n---@type SigilConfig\nlocal config = {\n\ttarget = {\n\t\t%s = %q,\n\t\tdefault = %q,\n\t},\n\tignore = {\n\t\t-- \"**/.DS_Store\",\n\t\t-- \"**/*.tmp\",\n\t\t-- \"cache/**\",\n\t},\n}\n\nreturn config\n", osKey, prettyTarget, prettyTarget)
-	return os.WriteFile(path, []byte(content), 0o644)
-}
-
-func promptWithDefault(reader *bufio.Reader, label, def string) string {
-	if def != "" {
-		fmt.Printf("%s [%s]: ", label, def)
-	} else {
-		fmt.Printf("%s: ", label)
-	}
-
-	text, _ := reader.ReadString('\n')
-	text = strings.TrimSpace(text)
-	if text == "" {
-		return def
-	}
-	return text
-}
-
-func promptYesNo(message string, def bool) (bool, error) {
-	reader := bufio.NewReader(os.Stdin)
-	defLabel := "y/N"
-	if def {
-		defLabel = "Y/n"
-	}
-	fmt.Printf("%s [%s]: ", message, defLabel)
-	text, err := reader.ReadString('\n')
-	if err != nil {
-		return false, err
-	}
-	text = strings.TrimSpace(strings.ToLower(text))
-	if text == "" {
-		return def, nil
-	}
-	return text == "y" || text == "yes", nil
-}
-
-func moveDirContents(srcDir, destDir string) error {
-	entries, err := os.ReadDir(srcDir)
-	if err != nil {
-		return err
-	}
-
-	for _, entry := range entries {
-		srcPath := filepath.Join(srcDir, entry.Name())
-		destPath := filepath.Join(destDir, entry.Name())
-
-		if _, err := os.Stat(destPath); err == nil {
-			return fmt.Errorf("destination already exists: %s", destPath)
-		} else if !errors.Is(err, os.ErrNotExist) {
-			return err
-		}
-
-		if err := os.Rename(srcPath, destPath); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-func findStaleLinks(filesDir, targetRoot string) ([]string, error) {
-	filesAbs, err := filepath.Abs(filesDir)
-	if err != nil {
-		return nil, err
-	}
-
-	var stale []string
-	walkErr := filepath.WalkDir(targetRoot, func(path string, entry fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-		if entry.IsDir() {
-			return nil
-		}
-
-		info, err := os.Lstat(path)
-		if err != nil {
-			return err
-		}
-		if info.Mode()&os.ModeSymlink == 0 {
-			return nil
-		}
-
-		src, err := os.Readlink(path)
-		if err != nil {
-			return err
-		}
-		if !filepath.IsAbs(src) {
-			src = filepath.Join(filepath.Dir(path), src)
-		}
-		src = filepath.Clean(src)
-
-		if !strings.HasPrefix(src, filesAbs+string(os.PathSeparator)) && src != filesAbs {
-			return nil
-		}
-
-		if _, err := os.Stat(src); errors.Is(err, os.ErrNotExist) {
-			stale = append(stale, path)
-		}
-		return nil
-	})
-
-	if walkErr != nil {
-		return nil, walkErr
-	}
-
-	return stale, nil
-}
-
-func findPackageByTarget(repo, targetRoot string) (string, error) {
-	repoEntries, err := os.ReadDir(repo)
-	if err != nil {
-		return "", err
-	}
-
-	absTarget, err := filepath.Abs(expandHome(targetRoot))
-	if err != nil {
-		return "", err
-	}
-
-	for _, entry := range repoEntries {
-		if !entry.IsDir() || strings.HasPrefix(entry.Name(), ".") {
-			continue
-		}
-
-		pkgDir := filepath.Join(repo, entry.Name())
-		configPath := filepath.Join(pkgDir, configFileName)
-		cfg, err := loadConfig(configPath)
-		if err != nil {
-			continue
-		}
-		target, err := selectTarget(cfg)
-		if err != nil {
-			if errors.Is(err, errTargetDisabled) {
-				continue
-			}
-			continue
-		}
-		absPkgTarget, err := filepath.Abs(expandHome(target))
-		if err != nil {
-			continue
-		}
-		if absPkgTarget == absTarget {
-			return entry.Name(), nil
-		}
-	}
-
-	return "", nil
-}
-
-func removeLinks(paths []string, dryRun bool) error {
-	for _, path := range paths {
-		if dryRun {
-			fmt.Printf("dry-run: remove %s\n", path)
-			continue
-		}
-		if err := os.Remove(path); err != nil {
-			return err
-		}
-		fmt.Printf("removed %s\n", path)
-	}
-	return nil
-}
-
-func handleStaleLinks(stales []string) error {
-	if len(stales) == 0 {
-		return nil
-	}
-
-	repo, err := repoPath()
-	if err != nil {
-		return err
-	}
-
-	reader := bufio.NewReader(os.Stdin)
-	for _, path := range stales {
-		fmt.Printf("stale: %s\n", path)
-
-		canUnlink, err := staleHasRepoFile(path, repo)
-		if err != nil {
-			return err
-		}
-
-		prompt := "action [p=prune, u=unlink, i=ignore]: "
-		if !canUnlink {
-			prompt = "action [p=prune, i=ignore]: "
-		}
-
-		fmt.Print(prompt)
-		choice, err := reader.ReadString('\n')
-		if err != nil {
-			return err
-		}
-		choice = strings.TrimSpace(strings.ToLower(choice))
-		if choice == "" || choice == "i" {
-			continue
-		}
-		if choice == "p" {
-			if err := os.Remove(path); err != nil {
-				return err
-			}
-			fmt.Printf("removed %s\n", path)
-			continue
-		}
-		if choice == "u" && canUnlink {
-			if err := unlinkStale(path, repo); err != nil {
-				return err
-			}
-			continue
-		}
-		fmt.Println("invalid choice; skipping")
-	}
-
-	return nil
-}
-
-func staleHasRepoFile(targetPath, repo string) (bool, error) {
-	repoPath, err := repoPathForTarget(targetPath, repo)
-	if err != nil {
-		return false, err
-	}
-	if repoPath == "" {
-		return false, nil
-	}
-	if _, err := os.Stat(repoPath); errors.Is(err, os.ErrNotExist) {
-		return false, nil
-	} else if err != nil {
-		return false, err
-	}
-	return true, nil
-}
-
-func unlinkStale(targetPath, repo string) error {
-	repoPath, err := repoPathForTarget(targetPath, repo)
-	if err != nil {
-		return err
-	}
-	if repoPath == "" {
-		return nil
-	}
-
-	if err := os.Remove(targetPath); err != nil {
-		return err
-	}
-
-	if err := copyFile(repoPath, targetPath); err != nil {
-		return err
-	}
-
-	if err := os.Remove(repoPath); err != nil {
-		return err
-	}
-
-	fmt.Printf("unlinked %s (removed %s)\n", targetPath, repoPath)
-	return nil
-}
-
-func repoPathForTarget(targetPath, repo string) (string, error) {
-	info, err := os.Lstat(targetPath)
-	if err != nil {
-		return "", err
-	}
-	if info.Mode()&os.ModeSymlink == 0 {
-		return "", nil
-	}
-
-	src, err := os.Readlink(targetPath)
-	if err != nil {
-		return "", err
-	}
-	if !filepath.IsAbs(src) {
-		src = filepath.Join(filepath.Dir(targetPath), src)
-	}
-	src = filepath.Clean(src)
-
-	repoAbs, err := filepath.Abs(repo)
-	if err != nil {
-		return "", err
-	}
-
-	rel, err := filepath.Rel(repoAbs, src)
-	if err != nil {
-		return "", err
-	}
-	if strings.HasPrefix(rel, "..") {
-		return "", nil
-	}
-
-	parts := strings.Split(rel, string(os.PathSeparator))
-	if len(parts) < 3 {
-		return "", nil
-	}
-	if parts[1] != filesDirName {
-		return "", nil
-	}
-
-	return filepath.Join(repoAbs, rel), nil
-}
-
-func restorePackage(filesDir, targetRoot string, dryRun bool) error {
-	filesAbs, err := filepath.Abs(filesDir)
-	if err != nil {
-		return err
-	}
-
-	return filepath.WalkDir(filesDir, func(path string, entry fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-		if path == filesDir {
-			return nil
-		}
-		if entry.IsDir() {
-			return nil
-		}
-
-		rel, err := filepath.Rel(filesDir, path)
-		if err != nil {
-			return err
-		}
-		targetPath := filepath.Join(targetRoot, rel)
-		return restoreOne(path, targetPath, filesAbs, dryRun)
-	})
-}
-
-func restorePath(filesDir, targetRoot, relPath string, dryRun bool) error {
-	filesAbs, err := filepath.Abs(filesDir)
-	if err != nil {
-		return err
-	}
-
-	relPath = filepath.Clean(relPath)
-	if strings.HasPrefix(relPath, "..") || filepath.IsAbs(relPath) {
-		return fmt.Errorf("invalid relative path %q", relPath)
-	}
-
-	sourcePath := filepath.Join(filesDir, relPath)
-	info, err := os.Lstat(sourcePath)
-	if err != nil {
-		return err
-	}
-
-	if info.IsDir() {
-		return filepath.WalkDir(sourcePath, func(path string, entry fs.DirEntry, err error) error {
-			if err != nil {
-				return err
-			}
-			if entry.IsDir() {
-				return nil
-			}
-			rel, err := filepath.Rel(filesDir, path)
-			if err != nil {
-				return err
-			}
-			targetPath := filepath.Join(targetRoot, rel)
-			return restoreOne(path, targetPath, filesAbs, dryRun)
-		})
-	}
-
-	rel, err := filepath.Rel(filesDir, sourcePath)
-	if err != nil {
-		return err
-	}
-	return restoreOne(sourcePath, filepath.Join(targetRoot, rel), filesAbs, dryRun)
-}
-
-func restoreOne(sourcePath, targetPath, filesAbs string, dryRun bool) error {
-	info, err := os.Lstat(targetPath)
-	if errors.Is(err, os.ErrNotExist) {
-		return nil
-	}
-	if err != nil {
-		return err
-	}
-	if info.Mode()&os.ModeSymlink == 0 {
-		return nil
-	}
-
-	src, err := os.Readlink(targetPath)
-	if err != nil {
-		return err
-	}
-	if !filepath.IsAbs(src) {
-		src = filepath.Join(filepath.Dir(targetPath), src)
-	}
-	src = filepath.Clean(src)
-
-	if !strings.HasPrefix(src, filesAbs+string(os.PathSeparator)) && src != filesAbs {
-		return nil
-	}
-
-	if dryRun {
-		fmt.Printf("dry-run: restore %s\n", targetPath)
-		return nil
-	}
-
-	if err := os.Remove(targetPath); err != nil {
-		return err
-	}
-
-	fmt.Printf("restored %s\n", targetPath)
-	return copyFile(sourcePath, targetPath)
-}
-
-func copyFile(src, dst string) error {
-	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
-		return err
-	}
-
-	srcFile, err := os.Open(src)
-	if err != nil {
-		return err
-	}
-	defer srcFile.Close()
-
-	info, err := srcFile.Stat()
-	if err != nil {
-		return err
-	}
-
-	dstFile, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, info.Mode())
-	if err != nil {
-		return err
-	}
-	defer dstFile.Close()
-
-	if _, err := io.Copy(dstFile, srcFile); err != nil {
-		return err
-	}
-
-	return nil
-}

ops.go

@@ -0,0 +1,402 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func applyPackage(filesDir, targetRoot string, cfg *packageConfig) error {
+	if err := ensureDir(targetRoot); err != nil {
+		return err
+	}
+
+	return filepath.WalkDir(filesDir, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if path == filesDir {
+			return nil
+		}
+
+		rel, err := filepath.Rel(filesDir, path)
+		if err != nil {
+			return err
+		}
+
+		if shouldIgnorePath(rel, cfg) {
+			if entry.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		targetPath := filepath.Join(targetRoot, rel)
+
+		if entry.IsDir() {
+			return ensureDir(targetPath)
+		}
+
+		srcAbs, err := filepath.Abs(path)
+		if err != nil {
+			return err
+		}
+		return linkFile(srcAbs, targetPath)
+	})
+}
+
+func linkFile(src, dst string) error {
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+
+	if info, err := os.Lstat(dst); err == nil {
+		if info.Mode()&os.ModeSymlink != 0 {
+			current, err := os.Readlink(dst)
+			if err != nil {
+				return err
+			}
+			if current == src {
+				return nil
+			}
+			return fmt.Errorf("conflict at %s (points to %s)", dst, current)
+		}
+		return fmt.Errorf("conflict at %s (exists and is not a symlink)", dst)
+	} else if !errors.Is(err, os.ErrNotExist) {
+		return err
+	}
+
+	return os.Symlink(src, dst)
+}
+
+func ensureDir(path string) error {
+	info, err := os.Lstat(path)
+	if err == nil {
+		if info.IsDir() {
+			return nil
+		}
+		return fmt.Errorf("%s exists and is not a directory", path)
+	}
+	if !errors.Is(err, os.ErrNotExist) {
+		return err
+	}
+	return os.MkdirAll(path, 0o755)
+}
+
+func findStaleLinks(filesDir, targetRoot string) ([]string, error) {
+	filesAbs, err := filepath.Abs(filesDir)
+	if err != nil {
+		return nil, err
+	}
+
+	var stale []string
+	walkErr := filepath.WalkDir(targetRoot, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if entry.IsDir() {
+			return nil
+		}
+
+		info, err := os.Lstat(path)
+		if err != nil {
+			return err
+		}
+		if info.Mode()&os.ModeSymlink == 0 {
+			return nil
+		}
+
+		src, err := os.Readlink(path)
+		if err != nil {
+			return err
+		}
+		if !filepath.IsAbs(src) {
+			src = filepath.Join(filepath.Dir(path), src)
+		}
+		src = filepath.Clean(src)
+
+		if !strings.HasPrefix(src, filesAbs+string(os.PathSeparator)) && src != filesAbs {
+			return nil
+		}
+
+		if _, err := os.Stat(src); errors.Is(err, os.ErrNotExist) {
+			stale = append(stale, path)
+		}
+		return nil
+	})
+
+	if walkErr != nil {
+		return nil, walkErr
+	}
+
+	return stale, nil
+}
+
+func removeLinks(paths []string, dryRun bool) error {
+	for _, path := range paths {
+		if dryRun {
+			fmt.Printf("dry-run: remove %s\n", path)
+			continue
+		}
+		if err := os.Remove(path); err != nil {
+			return err
+		}
+		fmt.Printf("removed %s\n", path)
+	}
+	return nil
+}
+
+func handleStaleLinks(stales []string) error {
+	if len(stales) == 0 {
+		return nil
+	}
+
+	repo, err := repoPath()
+	if err != nil {
+		return err
+	}
+
+	reader := newReader()
+	for _, path := range stales {
+		fmt.Printf("stale: %s\n", path)
+
+		canUnlink, err := staleHasRepoFile(path, repo)
+		if err != nil {
+			return err
+		}
+
+		prompt := "action [p=prune, u=unlink, i=ignore]: "
+		if !canUnlink {
+			prompt = "action [p=prune, i=ignore]: "
+		}
+
+		fmt.Print(prompt)
+		choice, err := reader.ReadString('\n')
+		if err != nil {
+			return err
+		}
+		choice = strings.TrimSpace(strings.ToLower(choice))
+		if choice == "" || choice == "i" {
+			continue
+		}
+		if choice == "p" {
+			if err := os.Remove(path); err != nil {
+				return err
+			}
+			fmt.Printf("removed %s\n", path)
+			continue
+		}
+		if choice == "u" && canUnlink {
+			if err := unlinkStale(path, repo); err != nil {
+				return err
+			}
+			continue
+		}
+		fmt.Println("invalid choice; skipping")
+	}
+
+	return nil
+}
+
+func staleHasRepoFile(targetPath, repo string) (bool, error) {
+	repoPath, err := repoPathForTarget(targetPath, repo)
+	if err != nil {
+		return false, err
+	}
+	if repoPath == "" {
+		return false, nil
+	}
+	if _, err := os.Stat(repoPath); errors.Is(err, os.ErrNotExist) {
+		return false, nil
+	} else if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+func unlinkStale(targetPath, repo string) error {
+	repoPath, err := repoPathForTarget(targetPath, repo)
+	if err != nil {
+		return err
+	}
+	if repoPath == "" {
+		return nil
+	}
+
+	if err := os.Remove(targetPath); err != nil {
+		return err
+	}
+
+	if err := copyFile(repoPath, targetPath); err != nil {
+		return err
+	}
+
+	if err := os.Remove(repoPath); err != nil {
+		return err
+	}
+
+	fmt.Printf("unlinked %s (removed %s)\n", targetPath, repoPath)
+	return nil
+}
+
+func restorePackage(filesDir, targetRoot string, dryRun bool) error {
+	filesAbs, err := filepath.Abs(filesDir)
+	if err != nil {
+		return err
+	}
+
+	return filepath.WalkDir(filesDir, func(path string, entry fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if path == filesDir {
+			return nil
+		}
+		if entry.IsDir() {
+			return nil
+		}
+
+		rel, err := filepath.Rel(filesDir, path)
+		if err != nil {
+			return err
+		}
+		targetPath := filepath.Join(targetRoot, rel)
+		return restoreOne(path, targetPath, filesAbs, dryRun)
+	})
+}
+
+func restorePath(filesDir, targetRoot, relPath string, dryRun bool) error {
+	filesAbs, err := filepath.Abs(filesDir)
+	if err != nil {
+		return err
+	}
+
+	relPath = filepath.Clean(relPath)
+	if strings.HasPrefix(relPath, "..") || filepath.IsAbs(relPath) {
+		return fmt.Errorf("invalid relative path %q", relPath)
+	}
+
+	sourcePath := filepath.Join(filesDir, relPath)
+	info, err := os.Lstat(sourcePath)
+	if err != nil {
+		return err
+	}
+
+	if info.IsDir() {
+		return filepath.WalkDir(sourcePath, func(path string, entry fs.DirEntry, err error) error {
+			if err != nil {
+				return err
+			}
+			if entry.IsDir() {
+				return nil
+			}
+			rel, err := filepath.Rel(filesDir, path)
+			if err != nil {
+				return err
+			}
+			targetPath := filepath.Join(targetRoot, rel)
+			return restoreOne(path, targetPath, filesAbs, dryRun)
+		})
+	}
+
+	rel, err := filepath.Rel(filesDir, sourcePath)
+	if err != nil {
+		return err
+	}
+	return restoreOne(sourcePath, filepath.Join(targetRoot, rel), filesAbs, dryRun)
+}
+
+func restoreOne(sourcePath, targetPath, filesAbs string, dryRun bool) error {
+	info, err := os.Lstat(targetPath)
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	if info.Mode()&os.ModeSymlink == 0 {
+		return nil
+	}
+
+	src, err := os.Readlink(targetPath)
+	if err != nil {
+		return err
+	}
+	if !filepath.IsAbs(src) {
+		src = filepath.Join(filepath.Dir(targetPath), src)
+	}
+	src = filepath.Clean(src)
+
+	if !strings.HasPrefix(src, filesAbs+string(os.PathSeparator)) && src != filesAbs {
+		return nil
+	}
+
+	if dryRun {
+		fmt.Printf("dry-run: restore %s\n", targetPath)
+		return nil
+	}
+
+	if err := os.Remove(targetPath); err != nil {
+		return err
+	}
+
+	fmt.Printf("restored %s\n", targetPath)
+	return copyFile(sourcePath, targetPath)
+}
+
+func copyFile(src, dst string) error {
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+
+	srcFile, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer srcFile.Close()
+
+	info, err := srcFile.Stat()
+	if err != nil {
+		return err
+	}
+
+	dstFile, err := os.OpenFile(dst, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, info.Mode())
+	if err != nil {
+		return err
+	}
+	defer dstFile.Close()
+
+	if _, err := io.Copy(dstFile, srcFile); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func moveDirContents(srcDir, destDir string) error {
+	entries, err := os.ReadDir(srcDir)
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range entries {
+		srcPath := filepath.Join(srcDir, entry.Name())
+		destPath := filepath.Join(destDir, entry.Name())
+
+		if _, err := os.Stat(destPath); err == nil {
+			return fmt.Errorf("destination already exists: %s", destPath)
+		} else if !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+
+		if err := os.Rename(srcPath, destPath); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

path.go

@@ -0,0 +1,244 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func repoPath() (string, error) {
+	if override := os.Getenv("SIGIL_REPO"); override != "" {
+		return filepath.Abs(expandHome(override))
+	}
+	return filepath.Abs(expandHome("~/.dotfiles"))
+}
+
+func expandHome(path string) string {
+	if path == "~" {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return path
+		}
+		return home
+	}
+	if strings.HasPrefix(path, "~/") {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return path
+		}
+		return filepath.Join(home, path[2:])
+	}
+	return path
+}
+
+func compressHome(path string) string {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return path
+	}
+	clean := filepath.Clean(path)
+	homeClean := filepath.Clean(home)
+	if clean == homeClean {
+		return "~"
+	}
+	if strings.HasPrefix(clean, homeClean+string(os.PathSeparator)) {
+		rel := strings.TrimPrefix(clean, homeClean+string(os.PathSeparator))
+		return filepath.Join("~", rel)
+	}
+	return path
+}
+
+func splitPackageSpec(spec string) (string, string, error) {
+	if spec == "" {
+		return "", "", errors.New("missing package")
+	}
+
+	parts := strings.SplitN(spec, ":", 2)
+	pkg := parts[0]
+	rel := ""
+	if len(parts) == 2 {
+		rel = parts[1]
+	}
+
+	pkg = strings.Trim(pkg, "/")
+	rel = strings.TrimPrefix(rel, "/")
+
+	if pkg == "" {
+		return "", "", errors.New("invalid package")
+	}
+
+	return pkg, rel, nil
+}
+
+func resolvePackageSpec(spec string) (string, string, error) {
+	repo, err := repoPath()
+	if err != nil {
+		return "", "", err
+	}
+
+	repoAbs, err := filepath.Abs(repo)
+	if err != nil {
+		return "", "", err
+	}
+
+	spec = expandHome(spec)
+	if filepath.IsAbs(spec) {
+		return resolvePathSpec(spec, repoAbs)
+	}
+
+	if strings.Contains(spec, string(os.PathSeparator)) {
+		return resolvePathSpec(spec, repoAbs)
+	}
+
+	clean := filepath.Clean(spec)
+	if strings.HasPrefix(clean, ".") || strings.HasPrefix(clean, string(os.PathSeparator)) {
+		return resolvePathSpec(clean, repoAbs)
+	}
+
+	return splitPackageSpec(spec)
+}
+
+func resolvePathSpec(pathSpec, repoAbs string) (string, string, error) {
+	absPath, err := filepath.Abs(pathSpec)
+	if err != nil {
+		return "", "", err
+	}
+
+	if strings.HasPrefix(absPath, repoAbs+string(os.PathSeparator)) || absPath == repoAbs {
+		rel, err := filepath.Rel(repoAbs, absPath)
+		if err != nil {
+			return "", "", err
+		}
+		parts := strings.Split(rel, string(os.PathSeparator))
+		if len(parts) >= 1 {
+			pkg := parts[0]
+			if len(parts) >= 2 && parts[1] == filesDirName {
+				relPath := filepath.Join(parts[2:]...)
+				return pkg, relPath, nil
+			}
+			return pkg, filepath.Join(parts[1:]...), nil
+		}
+	}
+
+	entries, err := os.ReadDir(repoAbs)
+	if err != nil {
+		return "", "", err
+	}
+
+	for _, entry := range entries {
+		if !entry.IsDir() || strings.HasPrefix(entry.Name(), ".") {
+			continue
+		}
+		pkgDir := filepath.Join(repoAbs, entry.Name())
+		configPath := filepath.Join(pkgDir, configFileName)
+		cfg, err := loadConfig(configPath)
+		if err != nil {
+			continue
+		}
+		targetRoot, err := selectTarget(cfg)
+		if err != nil {
+			if errors.Is(err, errTargetDisabled) {
+				continue
+			}
+			continue
+		}
+		absTarget, err := filepath.Abs(expandHome(targetRoot))
+		if err != nil {
+			continue
+		}
+		if strings.HasPrefix(absPath, absTarget+string(os.PathSeparator)) || absPath == absTarget {
+			rel, err := filepath.Rel(absTarget, absPath)
+			if err != nil {
+				return "", "", err
+			}
+			return entry.Name(), rel, nil
+		}
+	}
+
+	return "", "", fmt.Errorf("could not resolve %s to a package", pathSpec)
+}
+
+func findPackageByTarget(repo, targetRoot string) (string, error) {
+	repoEntries, err := os.ReadDir(repo)
+	if err != nil {
+		return "", err
+	}
+
+	absTarget, err := filepath.Abs(expandHome(targetRoot))
+	if err != nil {
+		return "", err
+	}
+
+	for _, entry := range repoEntries {
+		if !entry.IsDir() || strings.HasPrefix(entry.Name(), ".") {
+			continue
+		}
+
+		pkgDir := filepath.Join(repo, entry.Name())
+		configPath := filepath.Join(pkgDir, configFileName)
+		cfg, err := loadConfig(configPath)
+		if err != nil {
+			continue
+		}
+		target, err := selectTarget(cfg)
+		if err != nil {
+			if errors.Is(err, errTargetDisabled) {
+				continue
+			}
+			continue
+		}
+		absPkgTarget, err := filepath.Abs(expandHome(target))
+		if err != nil {
+			continue
+		}
+		if absPkgTarget == absTarget {
+			return entry.Name(), nil
+		}
+	}
+
+	return "", nil
+}
+
+func repoPathForTarget(targetPath, repo string) (string, error) {
+	info, err := os.Lstat(targetPath)
+	if err != nil {
+		return "", err
+	}
+	if info.Mode()&os.ModeSymlink == 0 {
+		return "", nil
+	}
+
+	src, err := os.Readlink(targetPath)
+	if err != nil {
+		return "", err
+	}
+	if !filepath.IsAbs(src) {
+		src = filepath.Join(filepath.Dir(targetPath), src)
+	}
+	src = filepath.Clean(src)
+
+	repoAbs, err := filepath.Abs(repo)
+	if err != nil {
+		return "", err
+	}
+
+	rel, err := filepath.Rel(repoAbs, src)
+	if err != nil {
+		return "", err
+	}
+	if strings.HasPrefix(rel, "..") {
+		return "", nil
+	}
+
+	parts := strings.Split(rel, string(os.PathSeparator))
+	if len(parts) < 3 {
+		return "", nil
+	}
+	if parts[1] != filesDirName {
+		return "", nil
+	}
+
+	return filepath.Join(repoAbs, rel), nil
+}

util.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+)
+
+type packageFlags struct {
+	dryRun bool
+}
+
+func parsePackageFlags(args []string) (packageFlags, string, error) {
+	flags := packageFlags{}
+	var pkg string
+	for _, arg := range args {
+		if arg == "--dry-run" {
+			flags.dryRun = true
+			continue
+		}
+		if strings.HasPrefix(arg, "-") {
+			return flags, "", fmt.Errorf("unknown flag %q", arg)
+		}
+		if pkg != "" {
+			return flags, "", errors.New("too many arguments")
+		}
+		pkg = arg
+	}
+	if pkg == "" {
+		return flags, "", errors.New("missing package")
+	}
+	return flags, pkg, nil
+}
+
+var stdinReader *bufio.Reader
+
+func newReader() *bufio.Reader {
+	if stdinReader == nil {
+		stdinReader = bufio.NewReader(os.Stdin)
+	}
+	return stdinReader
+}
+
+func promptWithDefault(label, def string) string {
+	reader := newReader()
+	if def != "" {
+		fmt.Printf("%s [%s]: ", label, def)
+	} else {
+		fmt.Printf("%s: ", label)
+	}
+
+	text, _ := reader.ReadString('\n')
+	text = strings.TrimSpace(text)
+	if text == "" {
+		return def
+	}
+	return text
+}
+
+func promptYesNo(message string, def bool) (bool, error) {
+	reader := newReader()
+	defLabel := "y/N"
+	if def {
+		defLabel = "Y/n"
+	}
+	fmt.Printf("%s [%s]: ", message, defLabel)
+	text, err := reader.ReadString('\n')
+	if err != nil {
+		return false, err
+	}
+	text = strings.TrimSpace(strings.ToLower(text))
+	if text == "" {
+		return def, nil
+	}
+	return text == "y" || text == "yes", nil
+}