fix(gitlab): drive self-hosted GitLab out-of-the-box with glab v1.5x

[karotkriss]

Summary

Makes no-mistakes drive a self-hosted GitLab instance out of the box for the direct branch -> MR flow, working with the current glab v1.5x CLI. No manual configuration beyond a normal glab auth login.

Problem

On a machine with glab v1.5x and more than one configured glab host, the pipeline pushed the branch but then silently skipped MR creation and never read CI - the run still reported success, so it looked like it shipped. Three version-driven incompatibilities caused it:

• Unscoped auth check. glab auth status (no host) checks every configured instance and exits non-zero if any has a stale token, so a healthy repo is judged unauthenticated and the MR step skips.
• Removed flag. glab mr list no longer accepts --state opened (open is the default in v1.5x); the unknown flag fails the whole command.
• Detached-HEAD worktree. The daemon checks out a commit, not a branch. glab ci get refuses to run there, so CI checks can never be read.

What this changes

1. Host-scoped auth - pass --hostname <host> to glab auth status so an unrelated instance's stale token can't poison this repo's check. Unknown host falls back to the unscoped check (fail-safe).
2. Drop removed --state - rely on glab mr list's open-by-default behavior instead of the flag that v1.5x removed.
3. Read CI jobs via glab api (REST) - when the project path is known, list jobs through glab api projects/<group%2Fproject>/pipelines/<id>/jobs. This is branch-independent (works in the detached-HEAD worktree), paginated, and maps finished_at into Check.CompletedAt for CI re-run detection. The legacy glab ci get path stays as a fallback when no project path is known.

Plus:

• Self-hosted detection - when a remote's hostname has no gitlab marker (e.g. git.example.com), consult glab's configured hosts (config.yml, honoring GLAB_CONFIG_DIR / XDG_CONFIG_HOME) and treat it as GitLab if the host matches a configured host or its api_host. Reads only user config, hardcodes nothing, and fails closed to unsupported.
• Project-path parser next to the Host - the new gitlab.ProjectPath lives in the gitlab backend package, mirroring github.RepoSlug.
• Positional constructor - gitlab.New(cmd, cliAvailable, host, projectPath), matching the GitHub backend's shape.

Compatibility

• Constructor is positional: New(cmd, cliAvailable, host, projectPath). Passing "", "" reproduces the legacy unscoped behavior.
• Unknown host -> unscoped auth check (fail-safe, unchanged behavior).
• A corrupt later page of paginated glab api output surfaces as an error rather than a silent partial that could hide a failed job.
• Fork MR routing for GitLab remains out of scope (unchanged).

Testing

• go test ./..., go vet ./..., and gofmt are clean.
• Verified live against a self-hosted GitLab with glab v1.53.0 and a multi-host glab config (one host carrying an unrelated stale token): the full push -> MR -> CI flow works end to end - host-scoped auth survives the stale token, the MR is created, and CI jobs are read via the paginated glab api path in the detached-HEAD worktree (MR mergeable, pipeline green).

[karotkriss]

@kunchenguid I had some problem using no-mistakes with my self-hosted GitLab repos so I thought I'd take the initiative and fixed it in this PR rather than just creating an issue.

This is one of the best tools I've ever integrated into my SDLC at work, I thank you for open sourcing this.

[kunchenguid]

Thanks for the contribution, @karotkriss! One process note on this repo: PRs need to be raised through no-mistakes (git push no-mistakes), which runs the review/test/lint/CI pipeline and stamps the required signature into the PR body. This PR is currently failing the "PR must be raised via no-mistakes" check because it wasn't raised that way.

If working from a fork was the blocker, that's fixed as of v1.30.0 (#306). Per CONTRIBUTING.md: point origin at this parent repo, run no-mistakes init --fork-url <your-fork-url>, then git push no-mistakes.

I won't be merging PRs that bypass the gate going forward, but I'd genuinely love to land your work once it's re-raised. Thanks for understanding! 🙏

[karotkriss]

Thanks for the contribution, @karotkriss! One process note on this repo: PRs need to be raised through no-mistakes (git push no-mistakes), which runs the review/test/lint/CI pipeline and stamps the required signature into the PR body. This PR is currently failing the "PR must be raised via no-mistakes" check because it wasn't raised that way.

If working from a fork was the blocker, that's fixed as of v1.30.0 (#306). Per CONTRIBUTING.md: point origin at this parent repo, run no-mistakes init --fork-url <your-fork-url>, then git push no-mistakes.

I won't be merging PRs that bypass the gate going forward, but I'd genuinely love to land your work once it's re-raised. Thanks for understanding! 🙏

Thank you for responding to my PR so quick, I will close this and reraise the pr to comply with the contribution guideline.