The town: a fake community across the pasture, checked for coherence

tools/pasture/town/ (run through tools/pasture/town.sh) seeds a fake
community across every running peer and checks that all of them, and
PrivaPub, agree on what happened:

- drivers per platform on four dialect bases (Mastodon API, Misskey API,
  Lemmy API, PrivaPub with /clientapi), each with a selftest against
  its own server; what a server holds is read from its database, never
  by making it fetch;
- a deterministic generator (specs/village.json: 23 accounts on seven
  servers, roots with several personas, circles and communities, a
  cross-server follow graph, posts of every kind and visibility, reply
  rounds, likes, boosts, reactions, votes, edits, deletes, blocks,
  mutes and a report) and a seeder that keeps a ledger of what happened;
- a sweep that expects delivery and confinement per server, what each
  account sees, counts, threads, edits, deletes, follows and privacy
  rows (sibling keys, published days, canary root credentials in every
  peer's database, located posts that never leave), with what the peers
  do on purpose modelled (Misskey drops orphan replies, Lemmy keeps only
  community content, edits go to the post's own audience);
- known gaps (gaps.json) turn failures into xfail and passes into xpass;
  a self-contained report.html, and docs/INTEROP-BACKLOG.md.

The pasture moves to a public-looking subnet (peers with no private
address switch can join), takes PASTURE_PORT when 6971 is in use, adds
peers to a running pasture (run.sh add, Caddy recreated with its CA
kept), removes its volumes on down, writes every scenario check to
out/scenarios.jsonl, serves decePub as decepub.test for its e2e tests,
lifts GoToSocial's and Lemmy's own rate limits, trusts Caddy in
Mastodon (TRUSTED_PROXY_IP) and gains Hollo (Fedify), whose one login
owning several accounts is the nearest peer to PrivaPub's personas.

The first village found the four PrivaPub bugs fixed in the commits
before this one; the second run, on the fixed server, passes 2319 checks
with 11 failures left, all between peers or from Lemmy's send worker,
which the seeder now warms up first. ROADMAP records the owner's
decisions of 2026-10-04 (the town, and P9 back from the cut list).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

tools/pasture/town/core/podman.py

@@ -0,0 +1,99 @@
+"""The pasture's containers from the workstation: commands, Postgres rows as JSON, Mongo documents as JSON, a copy of
+GoToSocial's sqlite. Only reads go through here; nothing a peer does is faked in its database."""
+import json
+import os
+import shutil
+import sqlite3
+import subprocess
+import tempfile
+
+
+def run(*args, input=None, check=True, timeout=300):
+	proc = subprocess.run(["podman", *args], input=input, capture_output=True, timeout=timeout,
+						  text=isinstance(input, str) or input is None)
+	if check and proc.returncode != 0:
+		raise RuntimeError(f"podman {' '.join(args[:3])}… failed: {proc.stderr.strip()[:500]}")
+	return proc.stdout
+
+
+def exec_(container, *cmd, input=None, check=True, timeout=300, workdir=None):
+	args = ["exec"]
+	if input is not None:
+		args.append("-i")
+	if workdir:
+		args += ["-w", workdir]
+	return run(*args, container, *cmd, input=input, check=check, timeout=timeout)
+
+
+def exists(container):
+	return subprocess.run(["podman", "container", "exists", container]).returncode == 0
+
+
+def running():
+	out = run("ps", "--format", "{{.Names}}")
+	return [n for n in out.split() if n.startswith("pasture-")]
+
+
+def psql(db, sql, *params):
+	"""Rows of `sql` as a list of dicts. Parameters are bound by psql (:'p1', :'p2'...), never pasted into the SQL."""
+	args = ["exec", "-i", "pasture-postgres", "psql", "-U", "pasture", "-d", db, "-tAX", "-v", "ON_ERROR_STOP=1"]
+	for i, p in enumerate(params, 1):
+		args += ["-v", f"p{i}={p}"]
+	wrapped = f"select coalesce(json_agg(t), '[]'::json) from ({sql.rstrip().rstrip(';')}) t;\n"
+	out = run(*args, input=wrapped)
+	return json.loads(out.strip() or "[]")
+
+
+def psql_value(db, sql, *params):
+	rows = psql(db, sql, *params)
+	if not rows:
+		return None
+	return next(iter(rows[0].values()))
+
+
+def mongo(js, db="PrivaPub"):
+	"""The JSON value of a mongosh expression, e.g. `db.Post.find({...}).toArray()`."""
+	script = f"print(EJSON.stringify(({js}), {{relaxed: true}}))"
+	out = run("exec", "pasture-mongo", "mongosh", "--quiet", db, "--eval", script, timeout=120)
+	return json.loads(out.strip().splitlines()[-1]) if out.strip() else None
+
+
+class SqliteCopy:
+	"""A consistent copy of a container's sqlite database (with its WAL), opened read-only on the workstation."""
+
+	def __init__(self, container, path):
+		self.dir = tempfile.mkdtemp(prefix="town-sqlite-")
+		local = os.path.join(self.dir, os.path.basename(path))
+		run("cp", f"{container}:{path}", local)
+		for suffix in ("-wal", "-shm"):
+			subprocess.run(["podman", "cp", f"{container}:{path}{suffix}", local + suffix], capture_output=True)
+		self.db = sqlite3.connect(local)
+		self.db.row_factory = sqlite3.Row
+
+	def rows(self, sql, *params):
+		return [dict(r) for r in self.db.execute(sql, params)]
+
+	def close(self):
+		self.db.close()
+		shutil.rmtree(self.dir, ignore_errors=True)
+
+	def __enter__(self):
+		return self
+
+	def __exit__(self, *exc):
+		self.close()
+
+
+def logs(container, since=None):
+	args = ["logs"]
+	if since:
+		args += ["--since", since]
+	return run(*args, container, check=False)
+
+
+def stats():
+	out = run("stats", "--no-stream", "--format", "json", *running(), check=False)
+	try:
+		return json.loads(out)
+	except ValueError:
+		return []