M3.3: the trust dial (the agent merges approved PRs)

A project's trust.merge is operator (the default) or approved (L3, D5,
#65). Set to approved, the harness, never the model, merges a PR in the
PR watch once an approving review from a gitea.operators account is on
its current commit, its checks pass (none at all counts; pending
waits) and it's mergeable; the item then goes on as after any merge.
Each reason to hold off (failed checks, conflicts, a refused merge) is
said once per commit.

Gitea enforces it: protection requires approvals from an operators-only
whitelist and dismisses stale ones. At start, for each approved
project, the agent checks by behaviour that its own unapproved merge is
refused, with a throwaway branch and PR made through the API (never the
workspace); if it isn't refused, the operator merges until a restart.

- gitea: approvals, combined check status, a PR's head commit and
  mergeability, API-made branches and their deletion.
- Test and bring-up repositories get the protection.
- Tests: the decision (unit), the hard wall on a real Gitea
  (test_trust_live), an e2e test where the operator only approves, and
  a walk property, merges_only_approved, checked against a mutant that
  ignores which commit was approved.

Closes #65

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

tests/integration/e2e_support.py

@@ -138,13 +138,20 @@ def make_repo(
             "POST",
             f"/repos/{full}/branch_protections",
             # Pushes only by the operator (who sets up fixtures, as an owner
-            # can); the agent's are refused, and merging needs an approval.
+            # can); the agent's are refused. Merging needs an approval only
+            # the operator can give, on the PR as it is now (D5, M3.3): the
+            # agent may merge once it has one.
             json={
                 "branch_name": "main",
                 "enable_push": True,
                 "enable_push_whitelist": True,
                 "push_whitelist_usernames": [OWNER],
                 "required_approvals": 1,
+                "enable_approvals_whitelist": True,
+                "approvals_whitelist_username": [OWNER],
+                "dismiss_stale_approvals": True,
+                "enable_merge_whitelist": True,
+                "merge_whitelist_usernames": [OWNER, agent],
             },
         )
         # The labels the agent reads (D1), as a project would have them.

tests/integration/test_end_to_end_loop.py

@@ -61,7 +61,9 @@ def running(
     ssh_host: SSHHost,
     tmp_path: Path,
     monkeypatch: pytest.MonkeyPatch,
+    request: pytest.FixtureRequest,
 ) -> Iterator[tuple[RunningLoop, InMemoryTransport, str]]:
+    mode = request.node.get_closest_marker("merge")
     run = uuid.uuid4().hex[:8]
     stack = contextlib.ExitStack()
     # Kept outside pytest's temp directories, which pytest prunes, so a
@@ -80,6 +82,7 @@ def running(
         push_key=fresh.push_key,
         workspace=Path(f"/tmp/nisse-e2e-{run}/sandbox"),
         build_host=build_host(ssh_host),
+        merge=mode.args[0] if mode else "operator",
     )
     config = replace(
         live_config,
@@ -229,6 +232,27 @@ class Operator:
         state = gitea._request("GET", f"/repos/{repo}/issues/{issue}")["state"]
         assert state == "closed"
 
+    def approve_and_wait(self, issue: int) -> None:
+        """Approve the item's PR, as the operator, and see the agent merge
+        it and close the item (trust.merge: approved)."""
+        gitea, repo = self.agent.gitea, self.agent.config.projects[0].repo
+        as_operator = operator_gitea(self.agent.config.gitea_url)
+        pr = loop_of(self.item(issue)).pr
+        as_operator._request(
+            "POST", f"/repos/{repo}/pulls/{pr}/reviews", json={"event": "APPROVED"}
+        )
+        deadline = time.monotonic() + DEADLINE_S
+        nudges = 0
+        while self.item(issue).status != "closed" and time.monotonic() < deadline:
+            self.tick()
+            if loop_of(self.item(issue)).wait == ANSWER:
+                nudges += 1
+                assert nudges <= MAX_ANSWERS, f"never closed: {self.last()}"
+                self.say("It's merged; please close the item.", issue)
+            self.settle()
+        assert gitea._request("GET", f"/repos/{repo}/pulls/{pr}")["merged"]
+        assert self.item(issue).outcome == "completed"
+
     def tidy(self, issues: list[int], prs: list[int]) -> None:
         """Leave the sandbox tidy: whatever is still open gets closed."""
         gitea, repo = self.agent.gitea, self.agent.config.projects[0].repo
@@ -690,3 +714,28 @@ def test_a_question_leaves_the_restatement_up(
         assert loop_of(operator.item(issues[0])).started
     finally:
         operator.tidy(issues, [])
+
+
+@pytest.mark.merge("approved")
+def test_an_approved_pr_is_merged_by_the_agent(
+    running: tuple[RunningLoop, InMemoryTransport, str],
+) -> None:
+    """M3.3: on a project set to merge approved PRs, the operator only
+    approves; the agent merges and closes the item."""
+    agent, transport, run = running
+    operator = Operator(agent, transport)
+    repo = agent.config.projects[0].repo
+    as_operator = operator_gitea(agent.config.gitea_url)
+    issue = None
+    pr = 0
+    try:
+        issue = as_operator.create_issue(repo, f"vowels_{run}", task(run))
+        as_operator.assign_issue(repo, issue, agent.account)
+        operator.tick()
+        item = operator.drive_until(MERGE, issue)
+        pr = loop_of(item).pr
+        operator.approve_and_wait(issue)
+        said = " ".join(m.text for m in transport.outbound)
+        assert f"Merged PR #{pr} after" in said
+    finally:
+        operator.tidy([issue] if issue is not None else [], [pr] if pr else [])

tests/integration/test_trust_live.py

@@ -0,0 +1,75 @@
+"""The trust dial's hard wall, on a real Gitea (D4, D5; M3.3): with the
+protection a `merge: approved` project has, the agent's own token can't
+merge its PR until an operator approves the PR as it is now; it can then;
+and a commit pushed after the approval needs approving again."""
+
+import base64
+import uuid
+from pathlib import Path
+
+import pytest
+from e2e_support import fresh_repo, operator_gitea
+
+from nisse_dev.config import AgentConfig
+from nisse_dev.gitea import GiteaClient, GiteaError
+
+pytestmark = pytest.mark.integration
+
+
+def add_file(gitea: GiteaClient, repo: str, branch: str, path: str) -> None:
+    gitea._request(
+        "POST",
+        f"/repos/{repo}/contents/{path}",
+        json={
+            "content": base64.b64encode(f"{path}\n".encode()).decode(),
+            "message": f"add {path}",
+            "branch": branch,
+        },
+    )
+
+
+def approve(operator: GiteaClient, repo: str, pr: int) -> None:
+    operator._request(
+        "POST", f"/repos/{repo}/pulls/{pr}/reviews", json={"event": "APPROVED"}
+    )
+
+
+def test_merging_needs_the_operators_approval_of_the_pr_as_it_is(
+    tmp_path: Path, live_config: AgentConfig, gitea: GiteaClient
+) -> None:
+    operator = operator_gitea(live_config.gitea_url)
+    run = uuid.uuid4().hex[:8]
+    with fresh_repo(operator, run, tmp_path / "keys", agent=gitea.whoami()) as repo:
+        name = repo.name
+        # The agent's PR, its branch made through the API.
+        gitea.branch_with_file(
+            name, base="main", branch="m-1", path="a.txt", text="a\n", message="a"
+        )
+        pr = gitea.open_pull_request(name, head="m-1", base="main", title="a", body="")
+        with pytest.raises(GiteaError):
+            gitea.merge_pull_request(name, pr.number)  # no approval yet
+
+        approve(operator, name, pr.number)
+        [approval] = gitea.approvals(name, pr.number)
+        head = gitea.pull_request(name, pr.number).head_sha
+        assert (approval.author, approval.commit) == (operator.whoami(), head)
+        gitea.merge_pull_request(name, pr.number)  # approved: the agent may
+        assert gitea.pull_request(name, pr.number).merged
+
+        # Approved, then changed: the approval no longer stands.
+        gitea.branch_with_file(
+            name, base="main", branch="m-2", path="b.txt", text="b\n", message="b"
+        )
+        second = gitea.open_pull_request(
+            name, head="m-2", base="main", title="b", body=""
+        )
+        approve(operator, name, second.number)
+        add_file(gitea, name, "m-2", "c.txt")  # a fix pushed after the approval
+        after = gitea.pull_request(name, second.number).head_sha
+        assert not [
+            a
+            for a in gitea.approvals(name, second.number)
+            if a.commit == after and not a.stale
+        ]
+        with pytest.raises(GiteaError):
+            gitea.merge_pull_request(name, second.number)