Multi-Repo vs. Monorepo: Cross-Language CI and Governance Integration

Direct Answers

Use path-filtered GitHub Actions workflows at repository root: one workflow per language runs only when files under that language’s directory change, while a separate governance workflow runs shared linting, security, and release checks on every push. Map each legacy team to a CODEOWNERS entry for its corresponding subdirectory, and enforce those owners through branch protection. Import each existing repository into a matching subdirectory with history preserved, archive the source repositories, and route new issues to the monorepo while leaving legacy issues in place unless you confirm an external tracker.

CI Architecture

Assumed layout:

algorithms/
  python/
  java/
  rust/
  go/
  .github/workflows/
    language-tests.yml
    governance.yml
  CODEOWNERS

In language-tests.yml, define one job per language and gate each with paths: so a change to python/ does not start Rust or Go jobs. In governance.yml, run shared checks such as license scanning, documentation freshness, and release-tag validation without language filters. This keeps per-language suite isolation while centralizing org-wide rules.

Maintainer Permissions and Review Routing

Create a root CODEOWNERS file that maps directories to teams:

# CODEOWNERS
/python/   @algorithms/python-maintainers
/java/     @algorithms/java-maintainers
/rust/     @algorithms/rust-maintainers
/go/       @algorithms/go-maintainers
/.github/  @algorithms/platform-engineering

Apply branch protection to the default branch and require approval from the CODEOWNERS team for any pull request touching their path. A Python contributor can still review Java code, but merge requires the Java team’s approval when java/ is changed.

Migration Path

1. Create the monorepo and add each legacy repository as a remote.
2. Fetch the legacy history and merge it into a language subdirectory using git merge --allow-unrelated-histories, optionally rewriting paths with a history-filtering tool before the merge.
3. Make legacy repositories read-only after the cutover date so contributors stop opening new pull requests there.
4. Redirect issue creation to the monorepo; link old issues from release notes or a migration index rather than closing them prematurely.

Verification

• Modify one file under python/ on a feature branch and confirm only the Python test job starts.
• Open a pull request changing rust/ without Rust team approval and confirm the required-review status remains pending.
• Run the import on a throwaway clone first to verify commit hashes and directory placement before updating the production monorepo.

Assumptions and Uncertainty

This answer assumes GitHub Actions is the CI platform and that repositories remain public, so minute consumption is not a constraint. The directory layout is a proposal, not an agreed standard. History import preserves commits but changes repository URLs; any external CI tokens or deploy keys must be reissued. Issue-tracking behavior depends on whether you use GitHub Issues or an external system.

Missing diagnostic detail: Do you track issues in GitHub Issues, or in an external tracker? That determines whether issue migration requires API synchronization or only a link from legacy repositories.