Feature request: sha and message body in changeset message

[nerdgore]

Hi, thanks for your great project.
While trying to set up changesets and conventional commits we discovered that there is one issue that may or may not be intentional that is breaking the changelog (for us).

When creating a PR with multiple comits we want to run changeset-conventional to create the changesets and add a comit to the PR. This works great, however, the only reference the changelogs have is the commit when the changesets have been added.

This means that if there is a PR that deals with multiple workspaces and dependency updates the log is not very helpful. The format used may drop essential information.

There are multiple options, depending on how far you want to go. I could also take a stab at implementing if you are willing to accept PRs. I have just briefly looked into the code and maybe this change is not necessary, given the has is already in the returned object. Basically we want to be able to generate a changelog like this:

[**scope**](link-to-repository?id=commitHash): feat: some message

The git command here could be updated to either be configurable or by default add all information to the changelog. This could open the tokens up to be used by a formatter - or simply return the message with the hash included (snas the regex magic) and use a changeset custom log format to do this.

const commitsWithMessages = commitsSinceBase.map((commitHash) => {
  const commitMessage = execSync(`git log -n 1 --pretty=format:%s\n\n%b ${commitHash}`)
  const [,type, scope, breaking, subject, body] = commitMessage.match(/([^(:]+)(?:\(([^)]+)\))?(!)?: (.+)(?:\n{2,}([\s\S]+))?/))
  return {
    commitData: { type, scope, breaking, subject, body },
    commitHash,
    commitMessage: 
  }
});

Let me know if I should elaborate more.

[iamchathu]

Please work on it. Current behaviour is not intentional and if we can make it better and useful, don't hesitate to contribute.