ci/lint: make push action have at least too commits depth

We see that when lint is called for push action git has only one last
commit which makes make indent with git-clang-format fail to operate.

Fix it by increasing fetch depth to one more commit.

Fixes: #2066
Fixes: d6db3333a ("clang-format: rework make indent to check specific commits")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

.github/workflows/lint.yml

@@ -23,6 +23,7 @@ jobs:
     - name: Run make indent
       run: >
         if [ -z "${{github.base_ref}}" ]; then
+          git fetch --deepen=1 &&
           if ! make indent OPTS=--diff; then
             exit 1
           fi