Source control: forge detection and linked pull requests across forges

[Tryanks]

Summary

Detect the git forge behind a project's remote and show the pull/merge request linked to each thread, for GitHub, GitLab, Gitea, Forgejo, Bitbucket and Azure DevOps, including self-hosted instances, using each forge's CLI where one exists.

Tcode today

Nothing forge-related exists: no remote get-url, no forge detection, no PR model (crates/services/src/git.rs only checks that a remote named origin exists). ureq is already a services dependency for REST fallbacks. The module doc of crates/core/src/git.rs says it "excludes PR/MR operations"; that is a derived comment and should be corrected with this work.

Associations (no model-facing tool)

T3 Code has two concepts; Tcode adopts both, minus T3's agent-facing MCP link tool (explicit non-goal):

• Branch PR: looked up automatically for the thread's branch (worktree path if any, else project root). One per thread, display-only, re-checked after each turn so a PR the agent opened with its own tools is found without any injection.
• Linked PRs: explicit links with a stored snapshot, several per thread (key {host, repo, number}). Sources: created (Tcode's own create-PR action, Source control: Open PR action usable during a run, with merge when CI passes #533) and manual (paste a URL, or "Link to thread" on a PR link in the transcript). Links win over the branch PR for display; unlinking falls back to the branch PR.
• Choosing a PR for a branch: skip unpublished branches; never match via an upstream that is the default branch; prefer open/draft, then most recently updated; require the head owner to match so fork PRs do not collide (GitLab and Forgejo reuse branch names, seen live).

Normalized model (crates/core)

ChangeRequest { forge, host, repo, number, url, title,
  state: Open | Draft | Merged | Closed,
  head_branch, head_owner: Option, base_branch, head_sha: Option,
  merged_at: Option, updated_at,
  checks: Option<Pending | Passing | Failing | NoChecks>,
  review: Option<Approved | ChangesRequested | Required | NoReview>,
  mergeable: Option<bool>, raw_state }

Forge detection order

1. Explicit user mapping (git host → forge kind + optional web/API host; the git host and web host can differ).
2. Known public hosts: github.com, *.ghe.com, gitlab.com, codeberg.org (Forgejo), gitea.com, bitbucket.org, dev.azure.com, *.visualstudio.com.
3. Hosts configured in the CLIs as the source of truth for self-hosted instances: gh auth status --json hosts, the hosts section of glab's config.yml, tea logins list -o json, fj's keys.json. (T3 Code has no refinement for GitHub Enterprise on domains without a github label; Tcode should.)
4. Unauthenticated probes, cached per host with a short timeout: /api/forgejo/v1/version 200 → Forgejo; /api/v1/version → Gitea; /api/v4/version 401 with x-gitlab-meta → GitLab; /api/v3/meta → GitHub Enterprise Server.

Normalize SSH hosts first (strip port, apply SSH config aliases and fj aliases).

Per-forge backends (crates/services/src/forge.rs, via the process helpers)

Forge	PR for branch	Pitfalls
GitHub / GHES	gh pr list -H X -s all --json …; checks via gh pr checks --json bucket	REST head= without owner: is silently ignored; reviewDecision is "" when not required
GitLab (incl. self-managed)	glab mr list --source-branch X -A -F json	mr view <branch> prompts on multiple matches; head_pipeline only on single-MR GET; glab auth status has no JSON
Gitea	tea api '/repos/{owner}/{repo}/pulls/BASE/OWNER:X'	tea pulls list cannot filter by branch; list JSON values are strings, no draft
Forgejo / Codeberg	REST /pulls?head=X&state=all (v16+), token from fj's keys.json or tea	fj has no JSON output; AGit PRs keep the branch in head.label
Bitbucket Cloud / DC	REST only (no official CLI); API tokens (app passwords ended 2026-06)	Repeat state=; defaults to OPEN
Azure DevOps	az repos pr list --source-branch X --status all -o json	Checks come from policy evaluations

Gerrit and SourceHut are out of scope (Gerrit cannot see local branch names; SourceHut has no PRs). Universal token fallback: git credential fill with GIT_TERMINAL_PROMPT=0.

Refresh

Host-side, with no client required: branch PR after each turn end and on branch/worktree changes; linked PRs sweep every minute (open PRs every minute, closed every 15 min, merged never unless requested); group by PR key so a PR shared by threads is read once; per-(forge, host, credential) rate-limit pauses honouring Retry-After, exponential backoff 30 s → 15 min. Missing or logged-out CLIs appear in Settings with the install/login hint; background lookups back off instead of looping.

UI

Sidebar badge (state glyph + number; +N for several links), thread header badge with checks and review glyphs, open in browser, link/unlink actions. Strings in both locales.

Reference

T3 Code origin/main: apps/server/src/sourceControl/*, ThreadPullRequestReactor.ts, PullRequestSyncReactor.ts, packages/shared/src/threadPullRequests.ts, migrations 042/048/050; #8160, #10101, #10839, #11436.