Add input manifest-file (#454)

Adds capability to maintain custom uv builds or to override the default
sources

.github/workflows/test.yml

@@ -533,6 +533,24 @@ jobs:
       - run: uv sync
         working-directory: __tests__/fixtures/old-python-constraint-project
 
+  test-custom-manifest-file:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install from custom manifest file
+        uses: ./
+        with:
+          version: 0.7.12-alpha.1
+          manifest-file: "https://raw.githubusercontent.com/astral-sh/setup-uv/${{ github.ref }}/__tests__/download/custom-manifest.json"
+      - run: uv sync
+        working-directory: __tests__/fixtures/uv-project
+      - name: Correct version gets installed
+        run: |
+          if [ "$(uv --version)" != "uv 0.7.12-alpha.1" ]; then
+            echo "Wrong uv version: $(uv --version)"
+            exit 1
+          fi
+
   all-tests-passed:
     runs-on: ubuntu-latest
     needs:
@@ -565,6 +583,7 @@ jobs:
       - test-tilde-expansion-cache-dependency-glob
       - cleanup-tilde-expansion-tests
       - test-no-python-version
+      - test-custom-manifest-file
     if: always()
     steps:
       - name: All tests passed