CI: fetch tags to make git-describe work

If git-describe fails, an empty string is assigned to CS_VERSION, which
breaks the regression tests that expect csdiff version to be available.

Author: kdudka

.github/workflows/ci.yml

@@ -25,6 +25,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v3
 
+      - name: Fetch tags to make git-describe work
+        run: git fetch --tags origin
+
       - name: '[clang] Install a default version for Ubuntu ${{ matrix.version }}'
         if: matrix.compiler == 'clang++'
         run: |