perf: add fast path for simple recursive globs (#2884)

internal/fsext/glob.go

@@ -0,0 +1,79 @@
+package fsext
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"github.com/go-task/task/v3/errors"
+)
+
+var errFastGlobFallback = errors.New("fast glob fallback")
+
+// FastRecursiveGlob expands simple literal-root recursive patterns. The
+// boolean reports whether the pattern was handled or requires the full shell
+// glob expander.
+func FastRecursiveGlob(pattern string) ([]string, bool, error) {
+	pattern = filepath.Clean(pattern)
+	separator := string(os.PathSeparator)
+	marker := separator + "**" + separator
+
+	idx := strings.Index(pattern, marker)
+	if idx == -1 || strings.Contains(pattern[idx+len(marker):], marker) {
+		return nil, false, nil
+	}
+
+	root := pattern[:idx]
+	namePattern := pattern[idx+len(marker):]
+	if root == "" || namePattern == "" || strings.Contains(namePattern, separator) {
+		return nil, false, nil
+	}
+	if strings.Contains(root, "**") || strings.ContainsAny(root, "*?[]{}") {
+		return nil, false, nil
+	}
+	if strings.ContainsAny(namePattern, "{}") {
+		return nil, false, nil
+	}
+
+	var results []string
+	err := filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			return nil
+		}
+		if path == root {
+			return errFastGlobFallback
+		}
+
+		if d.Type()&fs.ModeSymlink != 0 {
+			info, err := os.Stat(path)
+			if err != nil {
+				return err
+			}
+			if info.IsDir() {
+				return errFastGlobFallback
+			}
+		}
+
+		matched, err := filepath.Match(namePattern, d.Name())
+		if err != nil {
+			return err
+		}
+		if matched {
+			results = append(results, filepath.ToSlash(path))
+		}
+		return nil
+	})
+	if errors.Is(err, errFastGlobFallback) {
+		return nil, false, nil
+	}
+	if err != nil {
+		return nil, true, err
+	}
+	sort.Strings(results)
+	return results, true, nil
+}