ci: Enforce Conventional Commit messages

Author: Ware, Joseph (DLSLtd,RAL,LSCI)

.github/workflows/pr.yml

@@ -0,0 +1,14 @@
+name: PR Conventional Commit Validation
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, edited]
+
+jobs:
+  validate-pr-title:
+    runs-on: ubuntu-latest
+    steps:
+      - name: PR Conventional Commit Validation
+        uses:  ytanikin/[email protected]
+        with:
+          task_types: '["feat","fix","docs","test","ci","refactor","perf","chore","revert"]'

docs/explanations/decisions/0021-conventional-commits.md

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+# 3. Short descriptive title
+
+Date: 2025-04-07
+
+## Status
+
+Proposed
+
+## Context
+
+The template is in a period of both upheaval and uptake, where new users may adopt its use amidst major version changes.
+To give some certainty to users, we should document changes and highlight important ones.
+As dependency management becomes more automated, we should ensure that semantic versioning is used accurately, and make allowances for automation.
+
+## Decision
+
+Commits to the default branch of the copier template should be made using [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/), and the Conventional Commit standard should be used to identify the next released version and create changelogs/release notes.
+
+## Consequences
+
+A [GitHub Action](https://github.com/ytanikin/PRConventionalCommits) has been configured to ensure that PRs may not be merged without being in the form of a Conventional Commit.
+PRs will be squash-and-merged, with the complete git history of the change preserved in the PR but only a single commit on the default branch.
+PR commit messages will be taken from the title and body of the PR, ensuring that the commit will be compatible with the standard.
+Tooling (dependabot etc.) will be configured to make compatible PRs.