ENH: show diff of update constraint file (#24)

* ENH: colorize `uv pip install` output
* ENH: print diff with previous commit

action.yml

@@ -34,11 +34,16 @@ runs:
     - if: env.SETUP_FILE == 'pyproject.toml'
       run: |
         curl -LsSf https://astral.sh/uv/install.sh | sh
-        uv pip install --system update-pip-constraints@git+https://github.com/ComPWA/update-pip-constraints@v1
+        uv pip install --color=always --system update-pip-constraints@git+https://github.com/ComPWA/update-pip-constraints@v1
       shell: bash
 
     - run: update-pip-constraints --color
       shell: bash
+
+    - name: Show git diff
+      run: git diff --color --unified=0
+      shell: bash
+
     - uses: actions/upload-artifact@v4
       with:
         name: pip-constraints-${{ inputs.python-version }}