feat(commitlint): lint pull request titles

[SaiTejasJanjur-NV]

Description

The commitlint action can only lint commit ranges. This adds a pr-title input that lints a supplied pull request title instead.

This cannot be expressed with the existing inputs. commitlint reads a message on stdin only when --edit, --env, --from and --to are all omitted, and the run step emits --to "$COMMITLINT_TO" unconditionally with to defaulting to HEAD. Setting to: '' does not help either: the pipe is still discarded and git history is linted instead. So the title path is a separate branch that emits no range flags.

A pull request title is attacker-controlled free text, so it is bound through the step-level env: block and never interpolated into the run body.

Compatibility

Callers that do not set pr-title are unaffected. The input defaults to '', the range path is untouched, and the pre-change and post-change step bodies produce identical output and exit codes across every existing input combination listed below.

Validation

Both the pre-change and post-change Run commitlint step bodies were extracted from the parsed action.yml and executed under the composite shell GitHub uses, bash --noprofile --norc -e -o pipefail, against @commitlint/cli@21.2.2:

• pr-title set to a conventional title: exit 0, the title is linted
• pr-title set to Add Some Feature: exit 1, subject-empty and type-empty
• pr-title containing command substitution, backticks, quotes, semicolons and newlines: passed through as data, nothing executed and no file written
• pr-title set while from is also set: the title is linted and the range is ignored
• a failing commitlint inside the pipe fails the step: -e and pipefail abort before the branch's exit 0, so it cannot mask a failure
• no pr-title, across no inputs, from, to, config-file and from+to, in a normal clone, a shallow clone and an initial-commit repository: byte-identical output and exit codes before and after the change
• 12 titles run against the consumer's real config, including revert, merge, fixup!, bare-semver, acronym-leading, title-case and a 120-character header: exit codes identical to that repository's current inline invocation
• git diff --check origin/main...HEAD

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

Summary by CodeRabbit

• New Features

  • Added optional pull request title linting.
  • Pull request titles can now be checked directly without requiring full commit history.
  • Existing commit-range linting remains available when no title is provided.

• Documentation

  • Documented pull request title and commit-range linting behavior, including checkout-depth requirements.

[github-actions]

All contributors have signed the DCO ✍️ ✅
_{Posted by the DCO Assistant Lite bot.}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Enterprise

Run ID: b1548856-24fe-4482-b491-735d34270e35

📥 Commits

Reviewing files that changed from the base of the PR and between 3dda6f9 and 18e6a3b.

📒 Files selected for processing (2)

• .github/actions/commitlint/README.md
• .github/actions/commitlint/action.yml

Included review availability: Your plan provides up to 12 included reviews per hour; 11 remain after this review.

---

📝 Walkthrough

Walkthrough

The commitlint action now accepts an optional pull request title. When provided, it lints the title through standard input and skips commit-range linting. The README documents this mode and its checkout-history requirements.

Changes

Commitlint title linting

Layer / File(s)	Summary
Title linting flow .github/actions/commitlint/action.yml, .github/actions/commitlint/README.md	The action adds the pr-title input. It pipes the supplied title to commitlint, ignores from and to, and documents the different checkout requirements.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: huaweic-nv

Merge Risk: ⚪ Minimal · up to 18e6a

This change adds optional pull-request title linting while preserving existing commit-range behavior. No actionable merge-blocking risk remains after normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: adding pull request title linting to the commitlint action.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands.}

[SaiTejasJanjur-NV]

I have read the DCO Document and I hereby sign the DCO