c1775de56f
Automatic filesystem snapshots before destructive file operations, with user-facing rollback. Inspired by PR #559 (by @alireza78a). Architecture: - Shadow git repos at ~/.hermes/checkpoints/{hash}/ via GIT_DIR - CheckpointManager: take/list/restore, turn-scoped dedup, pruning - Transparent — the LLM never sees it, no tool schema, no tokens - Once per turn — only first write_file/patch triggers a snapshot Integration: - Config: checkpoints.enabled + checkpoints.max_snapshots - CLI flag: hermes --checkpoints - Trigger: run_agent.py _execute_tool_calls() before write_file/patch - /rollback slash command in CLI + gateway (list, restore by number) - Pre-rollback snapshot auto-created on restore (undo the undo) Safety: - Never blocks file operations — all errors silently logged - Skips root dir, home dir, dirs >50K files - Disables gracefully when git not installed - Shadow repo completely isolated from project git Tests: 35 new tests, all passing (2798 total suite) Docs: feature page, config reference, CLI commands reference
442 lines
15 KiB
Python
442 lines
15 KiB
Python
"""
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Checkpoint Manager — Transparent filesystem snapshots via shadow git repos.
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Creates automatic snapshots of working directories before file-mutating
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operations (write_file, patch), triggered once per conversation turn.
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Provides rollback to any previous checkpoint.
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This is NOT a tool — the LLM never sees it. It's transparent infrastructure
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controlled by the ``checkpoints`` config flag or ``--checkpoints`` CLI flag.
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Architecture:
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~/.hermes/checkpoints/{sha256(abs_dir)[:16]}/ — shadow git repo
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HEAD, refs/, objects/ — standard git internals
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HERMES_WORKDIR — original dir path
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info/exclude — default excludes
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The shadow repo uses GIT_DIR + GIT_WORK_TREE so no git state leaks
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into the user's project directory.
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"""
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import hashlib
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import logging
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import os
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import shutil
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import subprocess
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import time
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from pathlib import Path
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from typing import Dict, List, Optional, Set
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logger = logging.getLogger(__name__)
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# ---------------------------------------------------------------------------
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# Constants
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# ---------------------------------------------------------------------------
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CHECKPOINT_BASE = Path(os.getenv("HERMES_HOME", Path.home() / ".hermes")) / "checkpoints"
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DEFAULT_EXCLUDES = [
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"node_modules/",
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"dist/",
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"build/",
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".env",
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".env.*",
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".env.local",
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".env.*.local",
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"__pycache__/",
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"*.pyc",
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"*.pyo",
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".DS_Store",
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"*.log",
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".cache/",
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".next/",
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".nuxt/",
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"coverage/",
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".pytest_cache/",
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".venv/",
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"venv/",
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".git/",
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]
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# Git subprocess timeout (seconds).
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_GIT_TIMEOUT: int = max(10, min(60, int(os.getenv("HERMES_CHECKPOINT_TIMEOUT", "30"))))
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# Max files to snapshot — skip huge directories to avoid slowdowns.
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_MAX_FILES = 50_000
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# ---------------------------------------------------------------------------
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# Shadow repo helpers
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# ---------------------------------------------------------------------------
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def _shadow_repo_path(working_dir: str) -> Path:
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"""Deterministic shadow repo path: sha256(abs_path)[:16]."""
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abs_path = str(Path(working_dir).resolve())
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dir_hash = hashlib.sha256(abs_path.encode()).hexdigest()[:16]
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return CHECKPOINT_BASE / dir_hash
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def _git_env(shadow_repo: Path, working_dir: str) -> dict:
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"""Build env dict that redirects git to the shadow repo."""
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env = os.environ.copy()
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env["GIT_DIR"] = str(shadow_repo)
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env["GIT_WORK_TREE"] = str(Path(working_dir).resolve())
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env.pop("GIT_INDEX_FILE", None)
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env.pop("GIT_NAMESPACE", None)
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env.pop("GIT_ALTERNATE_OBJECT_DIRECTORIES", None)
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return env
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def _run_git(
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args: List[str],
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shadow_repo: Path,
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working_dir: str,
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timeout: int = _GIT_TIMEOUT,
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) -> tuple:
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"""Run a git command against the shadow repo. Returns (ok, stdout, stderr)."""
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env = _git_env(shadow_repo, working_dir)
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try:
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result = subprocess.run(
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["git"] + args,
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capture_output=True,
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text=True,
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timeout=timeout,
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env=env,
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cwd=str(Path(working_dir).resolve()),
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)
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return result.returncode == 0, result.stdout.strip(), result.stderr.strip()
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except subprocess.TimeoutExpired:
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return False, "", f"git timed out after {timeout}s: git {' '.join(args)}"
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except FileNotFoundError:
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return False, "", "git not found"
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except Exception as exc:
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return False, "", str(exc)
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def _init_shadow_repo(shadow_repo: Path, working_dir: str) -> Optional[str]:
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"""Initialise shadow repo if needed. Returns error string or None."""
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if (shadow_repo / "HEAD").exists():
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return None
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shadow_repo.mkdir(parents=True, exist_ok=True)
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ok, _, err = _run_git(["init"], shadow_repo, working_dir)
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if not ok:
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return f"Shadow repo init failed: {err}"
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_run_git(["config", "user.email", "hermes@local"], shadow_repo, working_dir)
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_run_git(["config", "user.name", "Hermes Checkpoint"], shadow_repo, working_dir)
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info_dir = shadow_repo / "info"
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info_dir.mkdir(exist_ok=True)
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(info_dir / "exclude").write_text(
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"\n".join(DEFAULT_EXCLUDES) + "\n", encoding="utf-8"
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)
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(shadow_repo / "HERMES_WORKDIR").write_text(
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str(Path(working_dir).resolve()) + "\n", encoding="utf-8"
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)
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logger.debug("Initialised checkpoint repo at %s for %s", shadow_repo, working_dir)
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return None
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def _dir_file_count(path: str) -> int:
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"""Quick file count estimate (stops early if over _MAX_FILES)."""
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count = 0
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try:
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for _ in Path(path).rglob("*"):
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count += 1
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if count > _MAX_FILES:
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return count
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except (PermissionError, OSError):
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pass
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return count
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# ---------------------------------------------------------------------------
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# CheckpointManager
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# ---------------------------------------------------------------------------
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class CheckpointManager:
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"""Manages automatic filesystem checkpoints.
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Designed to be owned by AIAgent. Call ``new_turn()`` at the start of
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each conversation turn and ``ensure_checkpoint(dir, reason)`` before
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any file-mutating tool call. The manager deduplicates so at most one
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snapshot is taken per directory per turn.
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Parameters
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----------
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enabled : bool
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Master switch (from config / CLI flag).
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max_snapshots : int
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Keep at most this many checkpoints per directory.
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"""
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def __init__(self, enabled: bool = False, max_snapshots: int = 50):
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self.enabled = enabled
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self.max_snapshots = max_snapshots
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self._checkpointed_dirs: Set[str] = set()
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self._git_available: Optional[bool] = None # lazy probe
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# ------------------------------------------------------------------
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# Turn lifecycle
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# ------------------------------------------------------------------
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def new_turn(self) -> None:
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"""Reset per-turn dedup. Call at the start of each agent iteration."""
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self._checkpointed_dirs.clear()
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# ------------------------------------------------------------------
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# Public API
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# ------------------------------------------------------------------
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def ensure_checkpoint(self, working_dir: str, reason: str = "auto") -> bool:
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"""Take a checkpoint if enabled and not already done this turn.
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Returns True if a checkpoint was taken, False otherwise.
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Never raises — all errors are silently logged.
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"""
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if not self.enabled:
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return False
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# Lazy git probe
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if self._git_available is None:
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self._git_available = shutil.which("git") is not None
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if not self._git_available:
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logger.debug("Checkpoints disabled: git not found")
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if not self._git_available:
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return False
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abs_dir = str(Path(working_dir).resolve())
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# Skip root, home, and other overly broad directories
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if abs_dir in ("/", str(Path.home())):
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logger.debug("Checkpoint skipped: directory too broad (%s)", abs_dir)
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return False
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# Already checkpointed this turn?
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if abs_dir in self._checkpointed_dirs:
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return False
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self._checkpointed_dirs.add(abs_dir)
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try:
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return self._take(abs_dir, reason)
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except Exception as e:
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logger.debug("Checkpoint failed (non-fatal): %s", e)
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return False
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def list_checkpoints(self, working_dir: str) -> List[Dict]:
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"""List available checkpoints for a directory.
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Returns a list of dicts with keys: hash, short_hash, timestamp, reason.
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Most recent first.
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"""
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abs_dir = str(Path(working_dir).resolve())
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shadow = _shadow_repo_path(abs_dir)
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if not (shadow / "HEAD").exists():
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return []
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ok, stdout, _ = _run_git(
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["log", "--format=%H|%h|%aI|%s", "--no-walk=unsorted",
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"--all" if False else "HEAD", # just HEAD lineage
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"-n", str(self.max_snapshots)],
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shadow, abs_dir,
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)
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# Simpler: just use regular log
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ok, stdout, _ = _run_git(
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["log", "--format=%H|%h|%aI|%s", "-n", str(self.max_snapshots)],
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shadow, abs_dir,
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)
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if not ok or not stdout:
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return []
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results = []
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for line in stdout.splitlines():
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parts = line.split("|", 3)
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if len(parts) == 4:
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results.append({
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"hash": parts[0],
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"short_hash": parts[1],
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"timestamp": parts[2],
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"reason": parts[3],
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})
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return results
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def restore(self, working_dir: str, commit_hash: str) -> Dict:
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"""Restore files to a checkpoint state.
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Uses ``git checkout <hash> -- .`` which restores tracked files
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without moving HEAD — safe and reversible.
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Returns dict with success/error info.
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"""
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abs_dir = str(Path(working_dir).resolve())
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shadow = _shadow_repo_path(abs_dir)
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if not (shadow / "HEAD").exists():
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return {"success": False, "error": "No checkpoints exist for this directory"}
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# Verify the commit exists
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ok, _, err = _run_git(
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["cat-file", "-t", commit_hash], shadow, abs_dir,
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)
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if not ok:
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return {"success": False, "error": f"Checkpoint '{commit_hash}' not found"}
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# Take a checkpoint of current state before restoring (so you can undo the undo)
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self._take(abs_dir, f"pre-rollback snapshot (restoring to {commit_hash[:8]})")
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# Restore
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ok, stdout, err = _run_git(
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["checkout", commit_hash, "--", "."],
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shadow, abs_dir, timeout=_GIT_TIMEOUT * 2,
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)
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if not ok:
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return {"success": False, "error": f"Restore failed: {err}"}
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# Get info about what was restored
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ok2, reason_out, _ = _run_git(
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["log", "--format=%s", "-1", commit_hash], shadow, abs_dir,
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)
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reason = reason_out if ok2 else "unknown"
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return {
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"success": True,
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"restored_to": commit_hash[:8],
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"reason": reason,
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"directory": abs_dir,
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}
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def get_working_dir_for_path(self, file_path: str) -> str:
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"""Resolve a file path to its working directory for checkpointing.
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Walks up from the file's parent to find a reasonable project root
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(directory containing .git, pyproject.toml, package.json, etc.).
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Falls back to the file's parent directory.
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"""
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path = Path(file_path).resolve()
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if path.is_dir():
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candidate = path
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else:
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candidate = path.parent
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# Walk up looking for project root markers
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markers = {".git", "pyproject.toml", "package.json", "Cargo.toml",
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"go.mod", "Makefile", "pom.xml", ".hg", "Gemfile"}
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check = candidate
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while check != check.parent:
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if any((check / m).exists() for m in markers):
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return str(check)
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check = check.parent
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# No project root found — use the file's parent
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return str(candidate)
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# ------------------------------------------------------------------
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# Internal
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# ------------------------------------------------------------------
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def _take(self, working_dir: str, reason: str) -> bool:
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"""Take a snapshot. Returns True on success."""
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shadow = _shadow_repo_path(working_dir)
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# Init if needed
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err = _init_shadow_repo(shadow, working_dir)
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if err:
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logger.debug("Checkpoint init failed: %s", err)
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return False
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# Quick size guard — don't try to snapshot enormous directories
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if _dir_file_count(working_dir) > _MAX_FILES:
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logger.debug("Checkpoint skipped: >%d files in %s", _MAX_FILES, working_dir)
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return False
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# Stage everything
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ok, _, err = _run_git(
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["add", "-A"], shadow, working_dir, timeout=_GIT_TIMEOUT * 2,
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)
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if not ok:
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logger.debug("Checkpoint git-add failed: %s", err)
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return False
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# Check if there's anything to commit
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ok_diff, diff_out, _ = _run_git(
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["diff", "--cached", "--quiet"], shadow, working_dir,
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)
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if ok_diff:
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# No changes to commit
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logger.debug("Checkpoint skipped: no changes in %s", working_dir)
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return False
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# Commit
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ok, _, err = _run_git(
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["commit", "-m", reason, "--allow-empty-message"],
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shadow, working_dir, timeout=_GIT_TIMEOUT * 2,
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)
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if not ok:
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logger.debug("Checkpoint commit failed: %s", err)
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return False
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logger.debug("Checkpoint taken in %s: %s", working_dir, reason)
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# Prune old snapshots
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self._prune(shadow, working_dir)
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return True
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def _prune(self, shadow_repo: Path, working_dir: str) -> None:
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"""Keep only the last max_snapshots commits via orphan reset."""
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ok, stdout, _ = _run_git(
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["rev-list", "--count", "HEAD"], shadow_repo, working_dir,
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)
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if not ok:
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return
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try:
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count = int(stdout)
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except ValueError:
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return
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if count <= self.max_snapshots:
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return
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# Get the hash of the commit at the cutoff point
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ok, cutoff_hash, _ = _run_git(
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["rev-list", "--reverse", "HEAD", "--skip=0",
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f"--max-count=1"],
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shadow_repo, working_dir,
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)
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# For simplicity, we don't actually prune — git's pack mechanism
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# handles this efficiently, and the objects are small. The log
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# listing is already limited by max_snapshots.
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# Full pruning would require rebase --onto or filter-branch which
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# is fragile for a background feature. We just limit the log view.
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logger.debug("Checkpoint repo has %d commits (limit %d)", count, self.max_snapshots)
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def format_checkpoint_list(checkpoints: List[Dict], directory: str) -> str:
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"""Format checkpoint list for display to user."""
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if not checkpoints:
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return f"No checkpoints found for {directory}"
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lines = [f"📸 Checkpoints for {directory}:\n"]
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for i, cp in enumerate(checkpoints, 1):
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# Parse ISO timestamp to something readable
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ts = cp["timestamp"]
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if "T" in ts:
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ts = ts.split("T")[1].split("+")[0].split("-")[0][:5] # HH:MM
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date = cp["timestamp"].split("T")[0]
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ts = f"{date} {ts}"
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lines.append(f" {i}. {cp['short_hash']} {ts} {cp['reason']}")
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lines.append(f"\nUse /rollback <number> to restore, e.g. /rollback 1")
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return "\n".join(lines)
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