Remove setup-git-user in favor of setting fallback only when identity is missing (#688)

* Experiment with skipping setup-git-user more often

* drop setup-git-user

* fix tests

README.md

@@ -18,7 +18,6 @@ There are also sub-actions hosted in this repository. Check out their respective
 - version-script - The command to update version, edit CHANGELOG, read and delete changesets. Default to `changeset version` if not provided
 - commit-message - The commit message to use. Default to `Version Packages`
 - pr-title - The pull request title. Default to `Version Packages`
-- setup-git-user - Sets up the git user for commits as `"github-actions[bot]"`. Default to `true`
 - create-github-releases - A boolean value to indicate whether to create Github releases after `publish` or not. Default to `true`
 - push-git-tags - A boolean value to indicate whether to create git tags after `publish` or not. Default to `true`
 - commit-mode - Specifies the commit mode. Use `"git-cli"` to push changes using the Git CLI, or `"github-api"` to push changes via the GitHub API. When using `"github-api"`, all commits and tags are GPG-signed and attributed to the user or app who owns the `GITHUB_TOKEN`. Default to `git-cli`
@@ -26,6 +25,11 @@ There are also sub-actions hosted in this repository. Check out their respective
 - pr-draft - Controls draft PR behavior. Use `create` to create new version PRs as draft, or `always` to also convert existing version PRs back to draft when updating them. By default, version PRs are not forced into draft mode
 - github-token - Passes a custom GitHub token
 
+Before creating local commits or annotated tags, the action preserves complete
+Git author and committer identities configured through the environment or Git
+configuration. If either identity is unavailable, it configures
+`github-actions[bot]` as a fallback.
+
 ### Outputs
 
 - published - A boolean value to indicate whether a publishing has happened or not