bump depth to 3

.github/workflows/build.yml

@@ -16,7 +16,11 @@ jobs:
       - name: Clone repository
         uses: actions/checkout@v1
         with:
-          fetch-depth: 1
+          # For an unknown reason fetch-depth: 1 breaks the "Re-run checks" button
+          # in Github Actions. With 1, the next build will fail on cloning with
+          # an error like this:
+          # ##[error]fatal: reference is not a tree: 1f9a2a
+          fetch-depth: 3
           submodules: true
 
       - name: Install rust