Support multiple `--config` files

[stephenmathieson]

I am using commit-and-tag-version in a monorepo. Each package in the monorepo has its own .versionrc.json file, which contains duplicated configuration (eg skip.tag=true, scripts.prerelease=...). Rather than needing to copy/paste this configuration into each package, it'd be nice if we could specify multiple config files and have their configuration merged together.

This could look something like:

packages/mypackage/package.json

{
  "scripts": {
    "release": "commit-and-tag-version -c ./.versionrc.json -c ../../.versionrc.json"
  }
}

packages/mypackage/.versionrc.json

{
  "path": ".",
  "tag-prefix": "mypackage@v",
  "releaseCommitMessageFormat": "chore(release): mypackage@{{currentTag}}"
}

.versionrc.json

{
  "scripts": {
    "prerelease": "./scripts/maybe-skip-release.sh"
  },
  "skip": {
    "tag": true
  }
}

It looks like implementing this would be reasonably simple, with minimal changes to lib/configuration.js. Is this something you'd be willing to support?