gc.md
markdown
| 1 | # `muse gc` — garbage-collect unreachable objects |
| 2 | |
| 3 | Muse stores every tracked file as a content-addressed blob under `.muse/objects/`. Over time — after branch deletions, abandoned experiments, or squash merges — blobs that are no longer reachable from any live commit accumulate and waste disk space. `muse gc` identifies and removes them. |
| 4 | |
| 5 | ## How it works |
| 6 | |
| 7 | 1. **Reachability walk**: Starting from every live branch head and tag, Muse walks the commit graph: |
| 8 | ``` |
| 9 | branch HEAD → CommitRecord → SnapshotRecord → manifest → object SHA-256 |
| 10 | ``` |
| 11 | 2. **Unreachable detection**: Any object *not* reachable from step 1 is garbage. |
| 12 | 3. **Deletion** (if not `--dry-run`): Unreachable objects are deleted. Empty prefix directories are also cleaned up. |
| 13 | |
| 14 | ## Usage |
| 15 | |
| 16 | ```bash |
| 17 | muse gc # remove unreachable objects (safe default) |
| 18 | muse gc --dry-run # show what would be removed without touching anything |
| 19 | muse gc --verbose # print each removed object ID |
| 20 | ``` |
| 21 | |
| 22 | ## Options |
| 23 | |
| 24 | | Flag | Default | Description | |
| 25 | |------|---------|-------------| |
| 26 | | `--dry-run`, `-n` | false | Preview only — no files are deleted | |
| 27 | | `--verbose`, `-v` | false | Print each collected object ID | |
| 28 | |
| 29 | ## Output |
| 30 | |
| 31 | ``` |
| 32 | Removed 12 object(s) (48.3 KiB) in 0.031s [247 reachable] |
| 33 | ``` |
| 34 | |
| 35 | In `--dry-run` mode: |
| 36 | |
| 37 | ``` |
| 38 | [dry-run] Would remove 12 object(s) (48.3 KiB) in 0.028s [247 reachable] |
| 39 | ``` |
| 40 | |
| 41 | ## Safety guarantees |
| 42 | |
| 43 | - The reachability walk always completes **before** any deletion begins. |
| 44 | - `--dry-run` is always safe to run — even in production, even by agents. |
| 45 | - GC never touches commit or snapshot records — only content blobs. |
| 46 | - Running GC is idempotent: running it twice produces the same result. |
| 47 | |
| 48 | ## When to run |
| 49 | |
| 50 | | Trigger | Recommendation | |
| 51 | |---------|---------------| |
| 52 | | After deleting branches | `muse gc` | |
| 53 | | Weekly CI maintenance | `muse gc --dry-run` to audit, then `muse gc` | |
| 54 | | Before `muse archive` | `muse gc` to shrink the repo | |
| 55 | | After a large squash merge | `muse gc` to free replaced blobs | |
| 56 | |
| 57 | ## Agent workflows |
| 58 | |
| 59 | ```bash |
| 60 | # Audit unreachable bloat before a deployment: |
| 61 | muse gc --dry-run |
| 62 | |
| 63 | # Automated nightly cleanup: |
| 64 | muse gc 2>&1 | logger -t muse-gc |
| 65 | ``` |
| 66 | |
| 67 | ## Exit codes |
| 68 | |
| 69 | | Code | Meaning | |
| 70 | |------|---------| |
| 71 | | 0 | Success (even if nothing was collected) | |
| 72 | | 1 | Internal error (corrupt store, permission issue) | |