CI: clone manually with /git base instead of actions/checkout

The instance generates clone URLs without its /git subpath, so
actions/checkout 404s. Manual clone against the correct base is the
reliable workaround until the server ROOT_URL is corrected.

.gitea/workflows/ci.yml

@@ -10,15 +10,16 @@ on:
 jobs:
   build-and-smoke:
     runs-on: ubuntu-latest
-    # This Gitea instance is served under the /git subpath, but act_runner
-    # reports GITHUB_SERVER_URL as https://octowow.st (subpath dropped), which
-    # makes actions/checkout (and API calls) build the wrong URL. Pin it.
-    # The real fix is the server's ROOT_URL = https://octowow.st/git/ (admin).
-    env:
-      GITHUB_SERVER_URL: https://octowow.st/git
     steps:
+      # octowow.st is served under /git, but Gitea generates clone URLs without
+      # it (ROOT_URL/proxy misconfig), so actions/checkout 404s. Clone manually
+      # against the correct base. Remove once the server ROOT_URL is fixed.
       - name: Checkout
-        uses: actions/checkout@v4
+        run: |
+          git init -q .
+          git remote add origin "https://gitea:${{ secrets.GITHUB_TOKEN }}@octowow.st/git/${{ github.repository }}.git"
+          git fetch -q --depth 1 origin "${{ github.ref }}"
+          git checkout -q FETCH_HEAD
 
       - name: Build image
         run: docker build -t mpq-packager:ci .