[php] How to force composer to reinstall a library?

I'm using the ZF2 skeleton app and it has a .gitignore that prevents external libraries from being commited to git. While debugging I like to go and change stuff here and there in the libraries' source to learn how things work. If these were version controlled it would be very easy to revert them back to their original state.

How can I force Composer to reinstall a particular framework so that I can get a fresh -unmodified- copy again?

PS: Please don't suggest removing the .gitignore file since it's there for a reason; it prevents my third party libraries from getting into my app's repository. I can always install them during an automated deployment.

I didn't want to delete all the packages in vendor/ directory, so here is how I did it:

1. rm -rf vendor/package-i-messed-up
2. composer install again

What I did:

1. Deleted that particular library's folder
2. composer update --prefer-source vendor/library-name

It fetches the library again along with it's git repo

As user @aaracrr pointed out in a comment on another answer probably the best answer is to re-require the package with the same version constraint.

ie.

composer require vendor/package

or specifying a version constraint

composer require vendor/package:^1.0.0

For some reason no one suggested the obvious and the most straight forward way to force re-install:

> composer remove vendor-name/package-name && composer vendor-name/package-name

Reinstall the dependencies. Remove the vendor folder (manually) or via rm command (if you are in the project folder, sure) on Linux before:

rm -rf vendor/

composer update -v

https://www.dev-metal.com/composer-problems-try-full-reset/

First execute composer clearcache

Then clear your vendors folder

rm -rf vendor/*

or better yet just remove the specific module which makes problems to avoid having to download all over again.