overby.me / oxidized-patch
A GNU patch-compatible diff application tool written in Rust
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README.md

Oxidized Patch #

Part of the overby.me monorepo, where this lives in safety/oxidized/patch and where all development happens.

It is also published on its own, as tangled.org/overby.me/oxidized-patch and github.com/overby-me/oxidized-patch. Both are read-only mirrors, rebuilt from the monorepo with josh: a commit made to either is overwritten by the next sync, so please open issues and pull requests on the monorepo.

A pure-Rust reimplementation of GNU patch(1) that aims to be output- compatible with the upstream tool. Passes 49/49 tests from the GNU patch 2.8 test suite.

Building #

nix build .#oxidized-patch
./result/bin/patch --help

A debug build is also available as .#oxidized-patch-dev for quick iteration.

Running the test suite #

Tests are run in a Nix sandbox. Each test script comes from the GNU patch source tarball; oxidized-patch is placed at $abs_top_builddir/src/patch and the script is executed against it.

# Run a single test
nix build .#checks.x86_64-linux.oxidized-patch-test-{name}

# View failure diff
nix log .#checks.x86_64-linux.oxidized-patch-test-{name}

See default.nix for the full list of test names. Tests time out after 60s.

Supported features #

All GNU patch 2.8 features exercised by the upstream test suite, including:

  • Unified, context, normal, and ed-style diffs (auto-detected)
  • Git extended headers: diff --git, new/deleted file mode, old/new mode, rename from/to, copy from/to, index, symlink mode (120000)
  • -p N path stripping (including -p0 and stripping empty)
  • -R reverse, -N/--forward, -f/--force, -t/--batch
  • -b/--backup with --backup-suffix, --backup-prefix, --basename-prefix, numbered/existing/simple backups via VERSION_CONTROL
  • --no-backup-if-mismatch, -E/--remove-empty-files
  • -o FILE with POSIX multi-patch concatenation
  • -i FILE, -d DIR, -r FILE (reject file)
  • --dry-run, --silent/-s, --verbose/-v
  • --read-only={ignore,warn,fail}
  • --reject-format={context,unified}, --posix, --binary
  • --follow-symlinks (writes a regular file, doesn't write through the link)
  • -e/--ed and auto-detection of ed-style input via positional file
  • --set-utc (parses YYYY-MM-DD HH:MM:SS + offset, updates mtime)
  • CRLF handling: per-file decision, --binary byte-exact mode, "different line endings" hunk-failure suffix
  • Fuzz/offset matching with GNU's asymmetric-context heuristic
  • Reject files in the matching format (or explicit --reject-format)
  • Shell-quoted filenames with embedded whitespace or meta-chars in diagnostics

Known limitations #

  • --merge (diff3-style conflict merging) is not implemented; invoking it exits with a "not implemented" error so the upstream merge test suite detects the absence and skips.
  • Interactive prompts (e.g. "Apply anyway? [n]") are emitted as static text and the implicit "no" is taken; -f/-t cover the non-interactive cases.
  • GIT binary payloads are recognised (the header is parsed) but the base85 delta is not decoded — the file is left unmodified and a diagnostic is printed.

Layout #

safety/oxidized/patch/
  Cargo.toml
  default.nix       # Nix package + test checks
  testsuite.nix     # Per-test Nix sandbox runner
  CHANGELOG.md
  README.md
  src/
    main.rs         # Single-file implementation