Switch the commit message check to gitlint in CI

This patch replaces the previous broken implementation [1] that was
using the `platisd/bad-commit-message-blocker` GitHub action with
manual calls of the `gitlint` tool.
The new implementation also attempts to expose the details of what is
being linted and adds the results to the workflow job summary. It
retrieves the number of the PR commits but no more than 50 and makes
sure to fetch all of them. If there's more, the workflow fails the
check as well.

[[1]]: platisd/bad-commit-message-blocker#12

.github/workflows/bad-commit-message-blocker.yml

@@ -1,19 +1,136 @@
 ---
 
-name: Good commit messages
+name: 📝 Git commit messages
 
 on:   # yamllint disable-line rule:truthy
   pull_request:
 
+env:
+  MAX_ALLOWED_PR_COMMITS: 50
+
 jobs:
   check-commit-message:
-    name: 📝
+    name: ✍
     if: github.event.pull_request.user.type != 'Bot'
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
-    - name: Verify commit messages follow best practices in CI
-      uses: platisd/[email protected]
+    - name: Get PR commits details
+      id: commits
+      run: |
+        COMMITS_NUMBER="$(\
+            2>http_headers curl --verbose --show-error \
+            --header 'Authorization: token ${{ secrets.GITHUB_TOKEN }}' \
+            --header 'Accept: application/vnd.github.v3+json' \
+            'https://api.github.com/repos/${{
+                github.repository
+            }}/pulls/${{
+                github.event.pull_request.number
+            }}/commits?per_page=${{
+                env.MAX_ALLOWED_PR_COMMITS
+            }}' | jq length \
+        )"
+        echo "number=${COMMITS_NUMBER}" >> "${GITHUB_OUTPUT}"
+
+        if grep 'link:' http_headers
+        then
+            TOO_MANY=true
+        else
+            TOO_MANY=false
+        fi
+        echo "too-many=${TOO_MANY}" >> "${GITHUB_OUTPUT}"
+
+        echo check-range='${{
+            github.event.pull_request.base.sha
+        }}..${{
+            github.event.pull_request.head.sha
+        }}' >> "${GITHUB_OUTPUT}"
+
+        echo last-commit='${{
+            github.event.pull_request.head.sha
+        }}' >> "${GITHUB_OUTPUT}"
+      shell: bash
+    - name: Prepare helper commands
+      id: commands
+      run: |
+        echo gitlint-install='pip install --user gitlint' >> "${GITHUB_OUTPUT}"
+
+        echo gitlint-lint="\
+        python -m \
+        gitlint.cli \
+        --ignore-stdin \
+        --commits '${{ steps.commits.outputs.check-range }}'\
+        " >> "${GITHUB_OUTPUT}"
+        # -C ./.github/workflows/.gitlint
+
+        echo git-log="\
+        git log --color --no-patch \
+        '${{ steps.commits.outputs.check-range }}'\
+        " >> "${GITHUB_OUTPUT}"
+      shell: bash
+    # Ref:https://joe.gl/ombek/blog/pr-gitlint/
+    - name: Check out src from Git
+      uses: actions/checkout@v3
       with:
-        github_token: ${{ secrets.GITHUB_TOKEN }}
+        fetch-depth: steps.commits.outputs.number
+        ref: ${{ github.event.pull_request.head.sha }}
+    - name: Log the commits to be checked
+      run: ${{ steps.commands.outputs.git-log }}
+    - name: Install gitlint
+      run: ${{ steps.commands.outputs.gitlint-install }}
+    - name: Check commit messages in the PR
+      shell: bash
+      run: |
+        >&2 echo Checking the following commit range: '${{
+            steps.commits.outputs.check-range
+        }}'
+        ${{
+            steps.commands.outputs.gitlint-lint
+        }} 2>&1 | >&2 tee gitlint-results.txt
+    - name: Report check summary for too many commits
+      if: fromJSON(steps.commits.outputs.too-many)
+      run: >-
+        echo
+        '# This pull request has too many commits, only the last ${{
+            env.MAX_ALLOWED_PR_COMMITS
+        }} have been checked'
+        >>
+        "${GITHUB_STEP_SUMMARY}"
+      shell: bash
+    - name: Set a failing status because of too many commits
+      if: fromJSON(steps.commits.outputs.too-many)
+      run: exit 1
+      shell: bash
+    - name: Report gitlint check summary
+      if: always()
+      run: |
+        echo >> "${GITHUB_STEP_SUMMARY}"
+        echo '# Gitlint check output' >> "${GITHUB_STEP_SUMMARY}"
+        echo >> "${GITHUB_STEP_SUMMARY}"
+
+        echo '```console' >> "${GITHUB_STEP_SUMMARY}"
+        echo "$ ${{
+            steps.commands.outputs.gitlint-install
+        }}" >> "${GITHUB_STEP_SUMMARY}"
+        echo "$ ${{
+            steps.commands.outputs.gitlint-lint
+        }}" >> "${GITHUB_STEP_SUMMARY}"
+        if ! grep 'Commit' gitlint-results.txt
+        then
+            echo 'Commit ${{
+                steps.commits.outputs.last-commit
+            }}:' >> "${GITHUB_STEP_SUMMARY}"
+        fi
+        cat gitlint-results.txt >> "${GITHUB_STEP_SUMMARY}"
+        echo '```' >> "${GITHUB_STEP_SUMMARY}"
+
+        echo >> "${GITHUB_STEP_SUMMARY}"
+        echo '# Checked commits' >> "${GITHUB_STEP_SUMMARY}"
+        echo >> "${GITHUB_STEP_SUMMARY}"
+        echo '```console' >> "${GITHUB_STEP_SUMMARY}"
+        ${{
+            steps.commands.outputs.git-log
+        }} --no-color >> "${GITHUB_STEP_SUMMARY}"
+        echo '```' >> "${GITHUB_STEP_SUMMARY}"
+      shell: bash
 
 ...