ci: create upcoming changelog via git-sv (#794)

https://github.com/thegeeklab/git-sv

- Creates a changelog from conventional commits
- Updates the changelog in an static issue (creates the issue if missing)
- Only runs after a new commit was merged into `main`
- Automatically determines the next version based on conv commits logic
- Follows up on #788

---

The logic can also be used to create the release notes on `tag` events and the subsequent Gitea release. Didn't wanted to add all at once, though.

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/794
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.com>
Co-authored-by: pat-s <patrick.schratz@gmail.com>
Co-committed-by: pat-s <patrick.schratz@gmail.com>

.gitea/workflows/changelog.yml

@@ -0,0 +1,28 @@
+name: changelog
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  changelog:
+    runs-on: ubuntu-latest
+    container: docker.io/thegeeklab/git-sv:1.0.11
+    steps:
+      - uses: actions/checkout@v4
+      - name: Generate upcoming changelog
+        run: |
+          apk add -q --no-cache curl jq sed
+          git sv rn -o changelog.md
+          export RELEASE_NOTES=$(cat changelog.md)
+          export ISSUE_NUMBER=$(curl -s "${{ gitea.event.repository.html_url }}/api/v1/repos/${{ gitea.repository }}/issues?state=open&q=Changelog%20for%20upcoming%20version" | jq '.[].number')
+
+          echo $RELEASE_NOTES
+          JSON_DATA=$(echo "" | jq -Rs --arg title 'Changelog for upcoming version' --arg body "$(cat changelog.md)" '{title: $title, body: $body}')
+
+          if [ -z "$ISSUE_NUMBER" ]; then
+            curl -s -X POST "${{ gitea.event.repository.html_url }}/api/v1/repos/${{ gitea.repository }}/issues?token=${{ secrets.ISSUE_RW_TOKEN }}" -H "Content-Type: application/json" -d "$JSON_DATA"
+          else
+            curl -s -X PATCH "${{ gitea.event.repository.html_url }}/api/v1/repos/${{ gitea.repository }}/issues/$ISSUE_NUMBER?token=${{ secrets.ISSUE_RW_TOKEN }}" -H "Content-Type: application/json" -d "$JSON_DATA"
+          fi