I'm using Microsoft Git-Credential-Manager for Linux (Ubuntu) for a couple weeks, with some credentials, and now I need to push modifications to a different repo with different credentials. But I can't do this, because GCM is trying to use incorrect data to access this repository.
How do I change these or add new ones in order to be able to commit to different repos with different credentials? Is it possible?
You can use git credential manager command to delete the entry for a given remote host.
git credential-manager reject <url>
Once the entry is deleted, you would be able to store new credentials.
You can store (git credential-manager store) one credential per host and user: that will be valid for all repos owned by said user.
For a credential per repository, as seen in Git-Credential-Manager-for-Windows/issue 749, use (for Windows or Linux) the git config credential.useHttpPath, explained in git credentials.
git config --global credential.useHttpPath true