{
  "id": 4466986,
  "title": "What \"undo\" actually means when the target is a real repo, not a fixture",
  "url": "https://urgent.news/2026/08/30/what-undo-actually-means-when-the-target-is-a-real-repo-not-a-fixture",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-08-30T17:27:16.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/mahirhir/what-undo-actually-means-when-the-target-is-a-real-repo-not-a-fixture-4l1c"
  },
  "original_language": "en",
  "account": "The claim made in the post asserts that a tool called \"gx\" can change a real, public Git repository, prove the change, undo it, and verify both the change and the undo offline, all within under 30 seconds. To disprove this claim, we cloned the github.com/stevemao/left-pad repository at commit 2fca615 and ran the four-stage walk on both the Git substrate and the file system (fs) substrate. If any stage failed, the wall-clock for either substrate's four stages exceeded 30 seconds, if the Git walk altered the worktree bytes of README.md, or if undo did not restore the exact pre-change SHA256 and HEAD, the claim would be incorrect. We ran the demonstration three times, and the results are shown in the table below.\n\nThe key observation is that, on the Git substrate, \"committing a change\" moves HEAD and creates a new blob in the object database without touching the bytes in the working tree. The file status shows as \"M README.md,\" indicating a modified file in the index/HEAD but the file bytes remain unchanged on disk. This is in contrast to the fs substrate, where committing a change directly rewrites the bytes on disk. The demo script utilizes separate string templates for each substrate, ensuring accurate reporting of the respective actions.",
  "summary": "Falsifier, stated before anything else Here's the claim this post makes, and here's exactly how to prove it wrong. Claim: a tool we built ( gx ) can take a real, public git repository, make a change to it through two different storage adapters, prove the change happened, undo it, and verify both the change and the undo (offline, in a separate process), and the whole four-stage walk finishes in…",
  "key_points": [
    "\"Undo\" tool claims to change, prove, undo, verify in <30 seconds",
    "Git substrate moves HEAD, creates new blob, leaves working tree unchanged",
    "File system substrate directly rewrites bytes on disk during commit"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}