Move diff generation workflow to this repository

This avoids issues with GitHub token permissions across pull requests from forks

.github/workflows/ci.yml

@@ -36,9 +36,9 @@ jobs:
           path: |
             deps
             _build
-          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}
+          key: ${{ runner.os }}-mix-${{matrix.pair.otp}}-${{ hashFiles('mix.lock') }}
           restore-keys: |
-            ${{ runner.os }}-mix-
+            ${{ runner.os }}-mix-${{matrix.pair.otp}}-
 
       - name: Check Code Format
         run: mix format --check-formatted
@@ -59,13 +59,3 @@ jobs:
           name: Results
           path: _build/test/lib/oapi_generator/*.xml
           reporter: java-junit
-
-  diff:
-    name: "Generate Diff"
-    runs-on: ubuntu-latest
-    steps:
-      - name: Dispatch Workflow
-        env:
-          GH_TOKEN: ${{ secrets.DIFF_TOKEN }}
-        run: |
-          gh workflow run generate.yml --repo aj-foster/open-api-diffs --field ref=$GITHUB_HEAD_REF

.github/workflows/generate.yml

@@ -0,0 +1,73 @@
+name: Generate
+
+on:
+  push:
+    branches:
+      - main
+  pull_request: {}
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: Ref of aj-foster/open-api-generator
+        required: true
+        type: string
+
+permissions:
+  contents: write
+
+jobs:
+  generate:
+    name: Generate Diff
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup Ref (Push)
+        if: github.event_name == 'pull_request'
+        run: |
+          echo "REF=main" >> $GITHUB_ENV
+
+      - name: Setup Ref (Pull Request)
+        if: github.event_name == 'pull_request'
+        run: |
+          echo "REF=$GITHUB_HEAD_REF" >> $GITHUB_ENV
+
+      - name: Setup Ref (Workflow Dispatch)
+        if: github.event_name == 'workflow_dispatch'
+        run: |
+          echo "REF=${{ inputs.ref }}" >> $GITHUB_ENV
+
+      - name: Checkout (Diffs)
+        uses: actions/checkout@v4
+        with:
+          repository: "aj-foster/open-api-diffs"
+          ref: main
+          path: diffs
+
+      - name: Checkout (Generator)
+        uses: actions/checkout@v4
+        with:
+          repository: "aj-foster/open-api-generator"
+          path: generator
+
+      - name: Setup BEAM
+        uses: erlef/setup-beam@v1
+        with:
+          otp-version: "27.0"
+          elixir-version: "1.17.1"
+
+      - name: Generate Code
+        run: |
+          cd diffs/
+          elixir generate.exs "$REF"
+
+      - name: Save Code
+        run: |
+          cd generator/
+          git checkout --orphan temporary-branch
+          git rm -rf .
+          mv ../diffs/output .
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add output/
+          git commit -m "Generated output for aj-foster/open-api-generator@$REF"
+          git tag -f "_diff/$REF"
+          git push --tags --force