Tool seems to try to (re)write files that don't contain matches

[08d2]

$ echo "hello world" > a.txt
$ echo "foo bar baz" > b.txt
$ chmod 400 b.txt
$ ruplacer 'hello' 'goodbye'
./a.txt:1 - hello world
./a.txt:1 + goodbye world

Would perform 1 replacement on 1 matching file
Re-run ruplacer with --go to write these changes to the filesystem
$ ruplacer 'hello' 'goodbye' --go
Error: Could not write ./b.txt

Caused by:
    Permission denied (os error 13)