This code only considers the first occurrence of each flag, which leads to no meaningful behavior, because all subsequent flags get ignored. This is demonstrably wrong:
$ cargo run -q --features cksum cksum -a md5 --binary --tag --untagged --binary README.md
e5773576fc75ff0f8eba14f61587ae28 README.md
$ cksum -a md5 --binary --tag --untagged --binary README.md
e5773576fc75ff0f8eba14f61587ae28 *README.md
Originally posted by @BenWiederhake in #6256 (comment)