src/Composer/IO/BaseIO.php
protected function checkAndSetAuthentication($repositoryName, $username, $password = null)
    {
        if ($this->hasAuthentication($repositoryName)) {
            $auth = $this->getAuthentication($repositoryName);
            if ($auth['username'] === $username && $auth['password'] === $password) {
                return;
            }

            $this->writeError(
                sprintf(
                    "<warning>Warning: You should avoid overwriting already defined auth settings for %s.</warning>",
                    $repositoryName
                )
            );
        }
        $this->setAuthentication($repositoryName, $username, $password);
    }
protected function checkAndSetAuthentication($repositoryName, $username, $password = null)
    {
        if ($this->hasAuthentication($repositoryName)) {
            $auth = $this->getAuthentication($repositoryName);
            if ($auth['username'] === $username && $auth['password'] === $password) {
                return;
            }

            $this->writeError(
                sprintf(
                    "<warning>Warning: You should avoid overwriting already defined auth settings for %s.</warning>",
                    $repositoryName
                )
            );
        }
        $this->setAuthentication($repositoryName, $username, $password);
    }
Check for overwrite and set the authentication information for the repository.

@param string $repositoryName The unique name of repository
@param string $username       The username
@param string $password       The password