CI: migrate to webhook bot and simplify labeler

This commit migrates the repository validation to a webhook-based bot instead of the GitHub Actions workflow (.github/workflows/formal.yml).

Since the bot handles stable branch labeling automatically (via the "branch_labeling: true" configuration option), the redundant branch check and labeling steps are removed from .github/workflows/labeler.yml.

The following configuration choices are applied in formalities.json:
- check_space_after_assignment: false (Disabled temporarily to catch any issues since it is a newly implemented check)
- check_makefile_indentation: false (Disabled temporarily to catch any issues since it is a new feature)
- check_patch_headers: 'warning' (Changed to warning instead of hard error since many legacy patches lack headers)
- enable_stale_bot: false (Disabled for now)

Other configurations can be adjusted in formalities.json based on the openwrt-bot-worker repository [1].

[1] https://github.com/openwrt/openwrt-bot-worker

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/24256
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

.github/formalities.json

@@ -0,0 +1,28 @@
+{
+  "check_branch": true,
+  "check_merge_commits": true,
+  "check_noreply_email": true,
+  "check_signoff": true,
+  "check_signature": true,
+  "allow_autosquash": true,
+  "enable_comments": true,
+  "max_subject_len_soft": 60,
+  "max_subject_len_hard": 80,
+  "max_body_line_len": 100,
+  "warn_duplicate_body": true,
+  "warn_generic_subjects": true,
+  "require_release_notes": true,
+  "check_pkg_version": true,
+  "check_crlf": true,
+  "add_package_label": true,
+  "drop_package_label": true,
+  "branch_labeling": true,
+  "check_openwrt_meta": true,
+  "check_conffiles": true,
+  "check_patch_headers": "warning",
+  "check_space_after_assignment": false,
+  "check_makefile_indentation": false,
+  "check_pkg_release": "warning",
+  "require_linked_github_account": true,
+  "enable_stale_bot": false
+}

.github/workflows/formal.yml

@@ -1,18 +0,0 @@
-name: Test Formalities
-
-on:
-  pull_request:
-
-permissions:
-  contents: read
-  pull-requests: write
-
-jobs:
-  build:
-    name: Test Formalities
-    uses: openwrt/actions-shared-workflows/.github/workflows/formal.yml@main
-    # with:
-    #   # Post formality check summaries to the PR.
-    #   # Repo's permissions need to be updated for actions to modify PRs:
-    #   # https://docs.github.com/en/rest/issues/comments?apiVersion=2022-11-28#create-an-issue-comment
-    #   post_comment: true

.github/workflows/labeler.yml

@@ -17,17 +17,3 @@ jobs:
       - uses: actions/labeler@v6
         with:
           repo-token: '${{ secrets.GITHUB_TOKEN }}'
-
-      - name: Check Branch
-        id: check-branch
-        run: |
-          if echo "${{ github.base_ref }}" | grep -q -E 'openwrt-[0-9][0-9]\.[0-9][0-9]'; then
-              echo "release-tag=$(echo ${{ github.base_ref }} | sed 's/openwrt-/release\//')" >> $GITHUB_OUTPUT
-          fi
-
-      - uses: buildsville/add-remove-label@v2.0.1
-        if: ${{ steps.check-branch.outputs.release-tag }}
-        with:
-          token: ${{secrets.GITHUB_TOKEN}}
-          labels: ${{ steps.check-branch.outputs.release-tag }}
-          type: add