fix: stop pruning the cached action ref on refresh (#1312)

The action cache refresh fetched with `--prune` and the unqualified refspec `+<ref>:refs/runner/<hash>`. Git cannot map that ref back to a remote ref, so it deleted it on every other refresh. The first job after a branch or tag moved then failed with `cannot lock ref`, and a moved tag in a full clone could silently run its old commit. `--no-prune` fixes this and also overrides an inherited `fetch.prune`.

Fixes: https://gitea.com/gitea/runner/issues/1311
Reviewed-on: https://gitea.com/gitea/runner/pulls/1312
Reviewed-by: Lunny Xiao <[email protected]>
Reviewed-by: Zettat123 <[email protected]>

e2e/testdata/workflows/action_ref.yml

@@ -0,0 +1,13 @@
+name: action-ref
+on:
+  workflow_dispatch:
+    inputs:
+      revision:
+        required: true
+jobs:
+  moving:
+    runs-on: e2e-action-ref
+    steps:
+      - uses: self:e2e-admin/e2e-moving-action@main
+        with:
+          revision: ${{ inputs.revision }}