Cover bounded reads and cancelled replacements

internal/fileops/read_bounded.go

@@ -3,6 +3,7 @@ package fileops
 import (
 	"fmt"
 	"io"
+	"math"
 	"os"
 	"strings"
 )
@@ -21,7 +22,11 @@ func ReadFileBounded(path string, limit int64) ([]byte, error) {
 		return nil, fmt.Errorf("open file %q: %w", path, err)
 	}
 	defer func() { _ = file.Close() }()
-	data, err := io.ReadAll(io.LimitReader(file, limit+1))
+	readLimit := limit
+	if limit < math.MaxInt64 {
+		readLimit++
+	}
+	data, err := io.ReadAll(io.LimitReader(file, readLimit))
 	if err != nil {
 		return nil, fmt.Errorf("read file %q: %w", path, err)
 	}