Code execution via untrusted repository config in auto-changelog

auto-changelog before 2.6.1 merges configuration from inside the target repository (the .auto-changelog file and the auto-changelog key in package.json) into its options, and honors security-sensitive options from that untrusted source. The handlebarsSetup option is passed to require(), so running auto-changelog over attacker-controlled repository content (for example, in a CI workflow that checks out an untrusted pull request head, or locally on a forked or third-party repository) executes attacker-chosen code with the privileges of the invoking user or CI job, including access to workflow secrets, without the repository dependencies ever being installed. The plugins option similarly loads attacker-controlled modules from the repository. Under the same conditions, appendGitLog/appendGitTag allow git argument injection (e.g. --output= to write arbitrary files), output allows writing attacker-influenced content to arbitrary paths, and template causes an outbound request to an attacker-chosen URL. Version 2.6.1 treats in-repository configuration as untrusted and refuses to run when it sets these options, unless the new --unsafe-config flag is passed.