test: add e2e tests with local Forgejo instance (#201)

* feat(forge): add new forge for forgejo

We only support repositories hosted on Forgejo instances, but not
Forgejo Actions or Woodpecker as CI solutions for now.

* test(e2e): introduce e2e test framework with local forgejo

.github/workflows/ci.yaml

@@ -35,6 +35,35 @@ jobs:
         uses: codecov/codecov-action@5a1091511ad55cbe89839c7260b706298ca349f7 # v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
+          flags: unit
+
+  test-e2e-forgejo:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Set up Go
+        uses: actions/setup-go@d35c59abb061a4a6fb18e82ac0862c26744d6ab5 # v5
+        with:
+          go-version-file: go.mod
+
+      # We can not use "jobs.<job>.services".
+      # We want to mount the config file, which is only available after "Checkout".
+      - name: Start Forgejo
+        working-directory: test/e2e/forgejo
+        run: docker compose up --wait
+
+      - name: Run tests
+        run: go test -tags e2e_forgejo -v -race -coverpkg=./... -coverprofile=coverage.txt  ./test/e2e/forgejo
+
+
+      - name: Upload results to Codecov
+        uses: codecov/codecov-action@18283e04ce6e62d37312384ff67231eb8fd56d24 # v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          flags: e2e
 
   go-mod-tidy:
     runs-on: ubuntu-latest