feat(bot): Коммит — навигация по дереву репозитория загрузок

- UploadsRepo: локальный клон, fetch не чаще fetch_interval, ls-tree -z (пробелы/кириллица),
  cat-file, последний коммит по пути; git без shell, ssh с -F /dev/null (без конфига хоста)
- «📝 Коммит»: папки/файлы с размерами, ⬆️ Вверх, страницы по 20, карточка файла
  с последним коммитом, «👁 Показать» (<pre> или документом); в кнопках только индексы
- ключ для контейнера: GIT_SSH_KEY_B64 → временный файл 0600 (смонтированный файл хоста
  контейнерному uid не прочитать); volume /data для клона
- тесты на настоящем bare-репозитории во временной папке

Refs #8

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/repo/git.py

@@ -0,0 +1,163 @@
+"""Local clone of the uploads repo and read-only queries against `origin/<branch>` (ARCHITECTURE §2.3).
+
+git runs as a subprocess with an argument list — never through a shell — and with the bot's own deploy key.
+"""
+
+import asyncio
+import base64
+import logging
+import os
+import tempfile
+import time
+from dataclasses import dataclass
+from datetime import datetime
+from pathlib import Path
+from typing import Literal
+
+from app.config import GitSettings
+
+log = logging.getLogger(__name__)
+
+EntryKind = Literal["dir", "file"]
+
+
+class GitError(Exception):
+    pass
+
+
+@dataclass(frozen=True)
+class Entry:
+    path: str  # repo-relative, "/"-separated
+    kind: EntryKind
+    size: int  # bytes; 0 for directories
+
+    @property
+    def name(self) -> str:
+        return self.path.rsplit("/", 1)[-1]
+
+
+@dataclass(frozen=True)
+class CommitInfo:
+    sha: str
+    author: str
+    date: datetime
+    subject: str
+
+
+class UploadsRepo:
+    def __init__(self, settings: GitSettings) -> None:
+        self._s = settings
+        self._dir = settings.clone_dir
+        self._lock = asyncio.Lock()
+        self._fetched_at: float | None = None
+        self._key_path = self._materialize_key()
+
+    @property
+    def ref(self) -> str:
+        return f"origin/{self._s.branch}"
+
+    @property
+    def path(self) -> Path:
+        return self._dir
+
+    def _materialize_key(self) -> Path | None:
+        if self._s.ssh_key_b64 is None:
+            return self._s.ssh_key_path
+        key = base64.b64decode(self._s.ssh_key_b64.get_secret_value())
+        fd, name = tempfile.mkstemp(prefix="tgit-ssh-")  # created 0600, owned by the bot's user
+        with os.fdopen(fd, "wb") as f:
+            f.write(key if key.endswith(b"\n") else key + b"\n")
+        return Path(name)
+
+    def _env(self) -> dict[str, str]:
+        env = {k: v for k, v in os.environ.items() if k in ("PATH", "HOME", "LANG", "LC_ALL", "TMPDIR")}
+        env["GIT_TERMINAL_PROMPT"] = "0"
+        if self._key_path is not None:
+            known_hosts = self._dir.parent / "known_hosts"
+            env["GIT_SSH_COMMAND"] = (
+                # -F /dev/null: ignore the host's ~/.ssh/config — otherwise a personal key configured there for the
+                # same host gets offered too and silently masks a broken deploy key (happened in #7).
+                f"ssh -F /dev/null -i {self._key_path} -o IdentitiesOnly=yes -o BatchMode=yes "
+                f"-o StrictHostKeyChecking=accept-new -o UserKnownHostsFile={known_hosts}"
+            )
+        return env
+
+    async def git(self, *args: str, cwd: Path | None = None) -> bytes:
+        proc = await asyncio.create_subprocess_exec(
+            "git",
+            *args,
+            cwd=cwd or self._dir,
+            env=self._env(),
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.PIPE,
+        )
+        try:
+            out, err = await asyncio.wait_for(proc.communicate(), timeout=self._s.timeout)
+        except TimeoutError:
+            proc.kill()
+            await proc.wait()
+            raise GitError(f"git {args[0]}: timeout") from None
+        if proc.returncode != 0:
+            raise GitError(f"git {args[0]}: {err.decode(errors='replace').strip()[-500:]}")
+        return out
+
+    async def ensure(self) -> None:
+        """Clone on first use; afterwards just make sure the clone is there."""
+        async with self._lock:
+            if (self._dir / ".git").is_dir():
+                return
+            self._dir.parent.mkdir(parents=True, exist_ok=True)
+            log.info("cloning uploads repo into %s", self._dir)
+            await self.git(
+                "clone", "--branch", self._s.branch, self._s.uploads_url, str(self._dir), cwd=self._dir.parent
+            )
+            self._fetched_at = time.monotonic()
+
+    async def refresh(self, force: bool = False) -> None:
+        """git fetch, but not more often than fetch_interval unless forced."""
+        await self.ensure()
+        async with self._lock:
+            now = time.monotonic()
+            if not force and self._fetched_at is not None and now - self._fetched_at < self._s.fetch_interval:
+                return
+            await self.git("fetch", "--prune", "origin")
+            self._fetched_at = now
+
+    async def head(self) -> str:
+        return (await self.git("rev-parse", self.ref)).decode().strip()
+
+    async def list_dir(self, path: str = "") -> list[Entry]:
+        """Directories first, then files, each alphabetically."""
+        spec = f"{self.ref}:{path}" if path else self.ref
+        try:
+            out = await self.git("ls-tree", "-z", "-l", spec)
+        except GitError as e:
+            raise GitError(f"no such directory: /{path}") from e
+        entries: list[Entry] = []
+        for record in out.split(b"\0"):
+            if not record:
+                continue
+            meta, name = record.split(b"\t", 1)
+            _mode, kind, _obj, size = meta.split()
+            full = f"{path}/{name.decode()}" if path else name.decode()
+            if kind == b"tree":
+                entries.append(Entry(full, "dir", 0))
+            elif kind == b"blob":
+                entries.append(Entry(full, "file", int(size)))
+        return sorted(entries, key=lambda e: (e.kind != "dir", e.name.lower()))
+
+    async def read(self, path: str) -> bytes:
+        return await self.git("cat-file", "blob", f"{self.ref}:{path}")
+
+    async def size(self, path: str) -> int | None:
+        try:
+            return int((await self.git("cat-file", "-s", f"{self.ref}:{path}")).decode().strip())
+        except GitError:
+            return None
+
+    async def last_commit(self, path: str) -> CommitInfo | None:
+        out = await self.git("log", "-1", "--format=%H%x00%an%x00%aI%x00%s", self.ref, "--", path)
+        if not out.strip():
+            return None
+        sha, author, date, subject = out.decode().rstrip("\n").split("\0", 3)
+        return CommitInfo(sha=sha, author=author, date=datetime.fromisoformat(date), subject=subject)