inject file directly

.github/workflows/flake-update.yml

@@ -51,7 +51,7 @@ jobs:
               id: upload-diff
               uses: actions/upload-artifact@v3
               with:
-                name: nix flake diff
+                name: nix-flake-diff.log
                 path: post-diff
                 compression-level: 9
                 if-no-files-found: error
@@ -61,25 +61,33 @@ jobs:
               with:
                 path: pr_body.template
                 contents: |
-                    - The following Nix Flake inputs were updated:
+                  - The following Nix Flake inputs were updated:
 
-                    ```
-                    ${{ env.UPDATE_LOG }}
-                    ```
+                  Flake input changes:
 
-                    Flake Diff can be found here:
-                    ${{ steps.upload-diff.outputs.artifact-url }}
+                  ```shell
+                  ${{ env.UPDATE_LOG }}
+                  ```
 
-                    Auto-generated by [update.yml][1] with the help of
-                    [create-pull-request][2].
+                  Flake evaluation diff:
 
-                    [1]: https://nayeonie.com/ahuston-0/nix-dotfiles/src/branch/main/.github/workflows/flake-update.yml
-                    [2]: https://forgejo.stefka.eu/jiriks74/create-pull-request
+                  ```shell
+                  nix-diff-placeholder
+                  ```
+
+                  Auto-generated by [update.yml][1] with the help of
+                  [create-pull-request][2].
+
+                  [1]: https://nayeonie.com/ahuston-0/nix-dotfiles/src/branch/main/.github/workflows/flake-update.yml
+                  [2]: https://forgejo.stefka.eu/jiriks74/create-pull-request
             - name: Generate PR body
               uses: pedrolamas/handlebars-action@v2.4.0 # v2.4.0
               with:
                 files: "pr_body.template"
                 output-filename: "pr_body.md"
+            - name: template diff into PR body
+              run: |
+                nix utils/inject-diff.py
             - name: Save PR body
               id: pr_body
               uses: juliangruber/read-file-action@v1