git_commit_subject_matches

Each commit’s subject line (the first line of its message) must match the matches: regex — the subject-grammar member of the commit family. Enforces a prefix + shape convention like go / Gerrit’s pkg/path: lowercase summary, node’s subsystem: description, or conventional-commit types. The regex is anchored to the subject alone (so ^…$ describes the first line exactly), unlike git_commit_message’s pattern: which matches the whole subject + body; for a subject-length cap use git_commit_message’s subject_max_length:. Shares the commit-validation family’s since: / include_merges: semantics and failure modes (HEAD-only when since: is unset, <since>..HEAD when set; silent outside a git repo; a bad since: ref hard-fails with a shallow-clone hint).

Options

Option	Type	Required	Default	Description
`include_merges`	boolean		`false`	When validating a range (`since:` set), include merge commits. Has no effect when `since:` is unset; combining `include_merges: true` with no `since:` is a load-time error.
`matches`	string	yes		Rust-regex the commit subject (first line of the message) must match.
`since`	string		`null`	Git ref to use as the base of the commit range. When set, validates every commit in `<since>..HEAD` instead of just HEAD. Use the canonical `{{env.X}}` interpolation to pass a SHA via an env var, e.g. `since: "{{env.ALINT_BASE_SHA \| default('origin/main')}}"`.

Plus the common level, id, and when fields. This rule analyses the whole repository, so it takes no paths. This table is generated from the JSON Schema; option types and defaults are authoritative.

Example

A commit subject that breaks the required grammar

The rule fires on this repository:

README.md

# demo

With this .alint.yml:

version: 1
rules:
  - id: subject-grammar
    kind: git_commit_subject_matches
    matches: '^[a-z0-9_/.-]+: [a-z].*$'
    level: error

committed with this history (oldest first):

2024-01-15T09:00:00+00:00  WIP: Capitalised and the wrong shape

alint check reports:

--- Repository-level -----------------------------------------------------------
  x  error    subject-grammar
              commit e103bea: subject does not match `^[a-z0-9_/.-]+: [a-z].*$`
              (subject: "WIP: Capitalised and the wrong shape")

Summary (1 violation):
  x 1 error
  0 passing * 1 failing

A commit subject that follows the `component: summary` grammar

This repository is compliant:

README.md

# demo