Add recursive directory search with depth limits

internal/engine/directory_walk.go

@@ -0,0 +1,50 @@
+package engine
+
+import (
+	"errors"
+	"io/fs"
+)
+
+var errImportDirectoryEntryLimit = errors.New("import directory-entry visit limit reached")
+
+// visitBoundedImportDirectory shares entry accounting across directory and glob searches.
+func visitBoundedImportDirectory(access *filesystemAccess, directory string, limit int, accounting *importAccounting, visit func(fs.DirEntry) error) error {
+	if accounting == nil {
+		accounting = &importAccounting{}
+	}
+	var visitError error
+	err := access.readDirectory(directory, func(entry fs.DirEntry) bool {
+		accounting.entries++
+		if accounting.entries > limit {
+			visitError = errImportDirectoryEntryLimit
+			return false
+		}
+		if err := visit(entry); err != nil {
+			visitError = err
+			return false
+		}
+		return true
+	})
+	if visitError != nil {
+		return visitError
+	}
+	return err
+}
+
+func importDirectoryEntryIsDirectory(entry fs.DirEntry) (bool, error) {
+	mode := entry.Type()
+	if mode&fs.ModeSymlink != 0 {
+		return false, nil
+	}
+	if mode.IsDir() {
+		return true, nil
+	}
+	if mode != 0 {
+		return false, nil
+	}
+	info, err := entry.Info()
+	if err != nil {
+		return false, err
+	}
+	return info.IsDir(), nil
+}