feat: Add ArgoCD diff workflow

.forgejo/workflows/argocd-diff-preview.yaml

@@ -0,0 +1,65 @@
+---
+name: ArgoCD Diff
+on:
+  workflow_dispatch:
+  workflow_call:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  argocd-diff-preview:
+    runs-on: docker
+    env:
+      PR_NUMBER: ${{ forge.event.pull_request.number }}
+    steps:
+      - uses: https://github.com/actions/checkout@v4
+        with:
+          path: pull-request
+
+      - uses: https://github.com/actions/checkout@v4
+        with:
+          ref: main
+          path: main
+
+      - name: Generate Diff
+        run: |
+          docker run \
+            --network=host \
+            -v /var/run/docker.sock:/var/run/docker.sock \
+            -v $(pwd)/main:/base-branch \
+            -v $(pwd)/pull-request:/target-branch \
+            -v $(pwd)/output:/output \
+            -e TARGET_BRANCH=refs/pull/$PR_NUMBER/merge \
+            -e REPO=${{ forge.repository }} \
+            dagandersen/argocd-diff-preview:v0.2.1
+
+      - name: Add comment
+        id: comment
+        if: always()
+        run: |
+          DIFF_BODY=$(cat output/diff.md)
+          payload="{\"body\": $DIFF_BODY}"
+
+          existing_comment=$(curl -s \
+            -H "Authorization: token ${{ secrets.FORGEJO_TOKEN }}" \
+            "${{ forge.api_url }}/repos/${{ forge.repository }}/issues/$PR_NUMBER/comments")
+          comment_id=$(echo "$existing_comment" | jq -r \
+            '.[] | select(.body | test("${{ forge.workflow }}")) | .id' | head -n 1)
+
+
+          if [ -n "${comment_id}" ] && [ "${comment_id}" != "null" ]; then
+            echo "Found comment with id ${comment_id}, updating..." && \
+            curl -s -X PATCH \
+              -H "Authorization: token ${{ secrets.FORGEJO_TOKEN }}" \
+              -H "Content-Type: application/json" \
+              "${{ forge.api_url }}/repos/${{ forge.repository }}/issues/comments/${comment_id}" \
+              -d "$payload"
+          else
+            echo "Creating new comment..." && \
+            curl -s -X POST \
+              -H "Authorization: token ${{ secrets.FORGEJO_TOKEN }}" \
+              -H "Content-Type: application/json" \
+              "${{ forge.api_url }}/repos/${{ forge.repository }}/issues/$PR_NUMBER/comments" \
+              -d "$payload"
+          fi