I'm going to post this, then post the answer since it drove me crazy until I figured out the issue.
When installing symfony/symfony via composer, the process was repeatedly aborting due to this error:
[RuntimeException]
Failed to execute git checkout 'fc0a09a2052e9275c16b5ab7af426935fe432f39' && git reset --hard 'fc0a09a2052e9275c16b5ab7af426935fe432f39'
error: Your local changes to the following files would be overwritten by checkout:
src/Symfony/Component/Validator/Resources/translations/validators.bg.xlf
Please, commit your changes or stash them before you can switch branches.
Aborting
I know it has something to do with git changing whitespace or line-endings on clone, then when it tries to checkout the specific commit, it fails since the line-endings have now been changed. git config core.autocrlf input
didn't help.