[](https://codecov.io/gh/iilei/gitsnitch)
# gitsnitch :dagger::goose:
**Lints your Git commit history against a declarative ruleset** — locally as a pre-commit/pre-push hook, or in any CI/CD pipeline.
Think of it as a linter, but for commit hygiene — enforced consistently across every author and every environment.
---
## Quick Start
### For developers (local linting)
Lint a single commit while iterating:
```sh
gitsnitch --commit-sha <sha>
```
With a preset bundle (e.g., enforce conventional commits):
```sh
gitsnitch --preset conventional-commits --commit-sha <sha>
```
### For CI/CD pipelines
Lint a range of commits in a pull request:
```sh
gitsnitch \
--source-ref "$GITHUB_HEAD_REF" \
--target-ref "origin/${GITHUB_BASE_REF}" \
--config .gitsnitch.toml \
--violation-severity-as-exit-code
```
Or lint via commit SHA with JSON output:
```sh
gitsnitch \
--commit-sha "$CI_COMMIT_SHA" \
--config .gitsnitch.toml \
--output-format json-compact
```
---
## Built-in Presets
Apply assertion bundles with `--preset` flags (repeatable):
* `conventional-commits` — enforce [Conventional Commits](https://www.conventionalcommits.org/)
* `title-body-separator` — require blank line between title and body
* `forbid-wip` — block WIP/DO NOT MERGE patterns
* `security-related-edits-mention` — require explicit mention of security in certain commit types
**Examples:**
```sh
gitsnitch --preset conventional-commits --preset forbid-wip --commit-sha <sha>
```
---
## Core Features
* **Message rules** — regex patterns on commit title, body, or full message
* **Diff rules** — restrict file paths, detect forbidden line patterns, enforce line-count thresholds
* **Context-aware skipping** — skip rules conditionally (e.g., on maintenance branches)
* **Severity bands** — map severity 0–250 to `Information`, `Warning`, `Error`, `Fatal`
* **Exit code mapping** — optionally map violation severity to exit code for CI automation
* **Shallow clone healing** — auto-deepen shallow CI checkouts
* **Remediation hints** — customizable Jinja2 banner templates per rule
* **Config autodiscovery** — find `.gitsnitch.toml`, `.gitsnitchrc`, `.gitsnitch.json`, etc., automatically
---
<details>
<summary><strong>Creating Custom Presets</strong></summary>
Presets provide assertion bundles (with optional assertion-level `banner` and `hint` templates) selected at runtime via CLI only.
**Rules:**
* Presets contain assertions only — no root-level `history`, `severity_bands`, or global switches
* Embedded at build-time from snake_case files
* Runtime names use dash-case (e.g., `conventional-commits`)
* Selected presets append to config assertions
* Assertion aliases must be globally unique; duplicates fail as a config error
**Authoring custom presets:**
Use the embedded preset files as templates:
* [src/presets_data/conventional_commits.toml](src/presets_data/conventional_commits.toml)
* [src/presets_data/title_body_separator.toml](src/presets_data/title_body_separator.toml)
* [src/presets_data/forbid_wip.toml](src/presets_data/forbid_wip.toml)
* [src/presets_data/security_related_edits_mention.toml](src/presets_data/security_related_edits_mention.toml)
Copy and adapt assertion blocks into your shared config file for project-local customization.
</details>
---
<details>
<summary><strong>Configuration & Input Modes</strong></summary>
### Choosing a lint scope
gitsnitch requires exactly one mode:
1. `--commit-sha <sha>` — lint a single commit
2. `--source-ref <ref> --target-ref <ref>` — lint a range between two refs
These are mutually exclusive. If neither is provided, gitsnitch fails with an explicit error.
### Config file autodiscovery
If no `--config` flag is given, gitsnitch searches the git repository root for config files in this order:
1. `.gitsnitch.toml`
2. `.gitsnitchrc` (TOML format, no extension)
3. `.gitsnitch.json`
4. `.gitsnitch.json5`
5. `.gitsnitch.yaml`
6. `.gitsnitch.yml`
The first match wins. If none is found, gitsnitch runs with no config (no assertions).
**Explicit config path:**
```sh
gitsnitch --config path/to/config.toml
```
**Read from stdin:**
```sh
### Config discovery root
By default, discovery searches the git repository root. Override it with:
```sh
GITSNITCH_CONFIG_ROOT=/path/to/config/dir gitsnitch
```
Or via flag:
```sh
gitsnitch --env-prefix CI_
# now reads CI_CONFIG_ROOT instead of GITSNITCH_CONFIG_ROOT
```
Custom namespace:
```sh
gitsnitch --env-prefix GITSNITCH_CUSTOM_NAMESPACE_
# reads GITSNITCH_CUSTOM_NAMESPACE_CONFIG_ROOT, etc.
```
</details>
---
<details>
<summary><strong>Runtime Inputs, Precedence & Environment Variables</strong></summary>
### precedence (CLI → env vars → config → defaults)
1. CLI flags (highest priority)
2. Environment variables (supported runtime keys only)
3. Config file values
4. Built-in defaults
### Supported environment variables
Canonical keys (default prefix `GITSNITCH_`):
* `GITSNITCH_CONFIG_ROOT` — where to search for config file
* `GITSNITCH_COMMIT_SHA` — commit to lint
* `GITSNITCH_SOURCE_REF` — source branch (for range linting)
* `GITSNITCH_TARGET_REF` — target branch (for range linting)
**Change the prefix:**
```sh
gitsnitch --env-prefix CI_
# reads CI_CONFIG_ROOT, CI_COMMIT_SHA, CI_SOURCE_REF, CI_TARGET_REF
```
**Remap to arbitrary env var names:**
```sh
gitsnitch \
--remap-env-var GITSNITCH_SOURCE_REF=PRE_COMMIT_TO_REF \
--remap-env-var GITSNITCH_TARGET_REF=PRE_COMMIT_FROM_REF
```
**Remap rules:**
* Format: `KEY=ENV_VAR`
* `ENV_VAR` must be non-empty
* A key can only be remapped once
* For a remapped key, only the remapped env var is read (no fallback)
* `--remap-env-var` is mutually exclusive with non-default `--env-prefix`
</details>
---
<details>
<summary><strong>Exit Codes & Output Formats</strong></summary>
### Exit code behavior
gitsnitch reserves exit codes `251..255` for internal/runtime failures.
Violation exit behavior is controlled by `violation_severity_as_exit_code`:
* `false` (default): violations are reported, exit is `0`
* `true`: exit code is the maximum violating assertion severity (0–250)
**Examples:**
* violations `{100, 200}` with mode `true` → exit `200`
* violations `{0, 0}` with mode `true` → exit `0`
* any violations with mode `false` → exit `0`
**CLI override:**
```sh
gitsnitch --violation-severity-as-exit-code ... # enable
gitsnitch --no-violation-severity-as-exit-code ... # disable (overrides config)
```
**Precedence:**
1. CLI flag (if provided)
2. config `violation_severity_as_exit_code`
3. default `false`
### Output formats
By default, `gitsnitch` renders pretty JSON:
```sh
gitsnitch --output-format json ...
```
Compact single-line JSON:
```sh
gitsnitch --output-format json-compact ...
```
Human-friendly text:
```sh
gitsnitch --output-format text-plain ...
```
Decorative terminal text:
```sh
gitsnitch --output-format text-decorative ...
```
Additionally write a JSON artifact to a file (without changing terminal output style):
```sh
gitsnitch --output-format text-decorative --gitsnitch-json report.json ...
```
`--gitsnitch-json` requires a real file path and does not accept `-`.
**Note:** terminal output honors `NO_COLOR` and `CI` to stay automation-friendly.
For machine-readable output, prefer `json` or `json-compact`.
</details>
---
<details>
<summary><strong>CI Authentication & Shallow Clone Autoheal</strong></summary>
When linting a ref range in a shallow checkout, `gitsnitch` may run `git fetch` to deepen history.
**Requirement:**
CI credentials must allow `git fetch` from `origin`.
**Common setups:**
* CI-native checkout token persisted for later fetches
* Git credential helper configured in the runner
* Optional `.netrc` file
**Example `.netrc`:**
```text
machine github.com
login x-access-token
password ${GITHUB_TOKEN}
```
Without credentials, shallow autoheal fetches fail and gitsnitch returns an internal/runtime error (`251..255`).
</details>
## Contributing
```sh
make install-tools
```
### Code-Quality
One-off run prek (1)
```sh
prek --stage manual --all-files
```
Install pre-commit, pre-push, and post-commit hooks
```sh
prek install
prek install --hook-type pre-push
prek install --hook-type post-commit
```
Configured automation highlights:
* `pre-push`: runs quality/security hooks and `make maintenance`
* `post-commit`: runs `make generate-coverage`
---
1) [prek quote](https://prek.j178.dev/):
<blockquote>
prek is a reimagined version of pre-commit, built in Rust. It is designed to be a faster, dependency-free and drop-in alternative for it, while also providing some additional long-requested features.
</blockquote>
