ci: cz: only check PR commits

Once something is merged, it does not make sense (and it's too late) to
check it.

So, limit the check to commits in a given PR.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

.github/workflows/ci.yml

@@ -28,12 +28,12 @@ jobs:
       run: go test -test.v -race -cover ./...
 
   conventional-commits:
+    if: github.event_name == 'pull_request' # Only check PRs.
     runs-on: ubuntu-latest
 
     steps:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
     - run: pip3 install -U Commitizen
-      # The commit hash here is that of the commit where we started using conventional commits.
-    - run: cz check --rev-range deebab92..HEAD
+    - run: cz check --rev-range origin/${{ github.base_ref }}..HEAD