How to modify the package root or exclude folder in composer?

I am now a GitHub repo folder structure is this:

foo/bar/abc/   composer.json   lib/   test/

I want to publish the ABC library on the packagist, but it seems like I can only publish the whole repo all at once. And,, and foo bar test so on are useless folders. How do I set ABC to the root directory at the time of publication and exclude Test?

There is also a premise that these folders are found in Git repo, but it is best not to appear on packagist.

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I am now a GitHub repo folder structure is this:

foo/bar/abc/   composer.json   lib/   test/

I want to publish the ABC library on the packagist, but it seems like I can only publish the whole repo all at once. And,, and foo bar test so on are useless folders. How do I set ABC to the root directory at the time of publication and exclude Test?

There is also a premise that these folders are found in Git repo, but it is best not to appear on packagist.

How do I feel this should not be about composer, it's Git's problem? Just use it .gitignore to get rid of the relevant folder before submitting it.

Use git filter-branch or git subtree split command to cut out the ABC directory and submit it separately as a repo

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