René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"pre-commit can delete/revert unstaged files if error occurs during git diff-index","articleBody":"### search you tried in the issue tracker\n\ndiff-index\n\n### describe your issue\n\nI performed a git commit with some modifications unstaged.  After the commit, most of the modifications had been reverted and my work was lost.  The diff saved in the patch directory had only a few of the modifications in - the ones that survived. The rest were gone.\r\n\r\nTo reproduce:\r\n- Modify four files and stage one with `git add`\r\n- Use `git status` to determine the order of the three unstaged files.\r\n- Change the permission on the middle one so that git will not be able to read it\r\n- Now do `git commit`: the changes to the first unstaged file will be preserved but the other two will be lost.\r\n\r\nThe key point, I think, is that the code in `staged_files_only.py` checks that the return code when creating the diff is non-zero which it takes to mean that the code is `1` meaning that there were diffs.   However, in this case the return code is `128` which *is* non-zero but does _not_ mean success - it means error.  So the code assumes the diff is OK even though it is incomplete.\n\n### pre-commit --version\n\n2.17.0\n\n### .pre-commit-config.yaml\n\n```yaml\nrepos:\r\n- repo: https://github.com/pre-commit/pre-commit-hooks\r\n  rev: 56b4a7e506901ff86f8de5c2551bc41f8eacf717\r\n  hooks:\r\n     -   id: check-yaml\r\n#     -   id: end-of-file-fixer\r\n     -   id: trailing-whitespace\r\n- repo: https://github.com/psf/black\r\n  rev: 21.11b0\r\n  hooks:\r\n    -   id: black\r\n        language_version: python3.6\r\n- repo: https://github.com/PyCQA/isort\r\n  rev: 5.10.1\r\n  hooks:\r\n    -   id: isort\r\n        args: [\"--profile\", \"black\", \"--filter-files\"]\n```\n\n\n### ~/.cache/pre-commit/pre-commit.log (if present)\n\n_No response_","author":{"url":"https://github.com/strubbly","@type":"Person","name":"strubbly"},"datePublished":"2023-02-21T16:18:01.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/2773/pre-commit/issues/2773"}