cd: update the packaging workflow strategy

Before, we create and publish packages only when tag has been pushed,
now we try to create packages for each PR and publish them only when
tag has been pushed.

Author: LeonidVas

.github/workflows/packaging.yml

@@ -1,12 +1,14 @@
 name: packaging
 
-on:
-  push:
-    tags:
-      - '*'
+on: [push, pull_request]
 
 jobs:
   package:
+    # Skip pull request jobs when the source branch is in the same
+    # repository.
+    if: |
+      github.event_name == 'push' ||
+      github.event.pull_request.head.repo.full_name != github.repository
     runs-on: ubuntu-latest
 
     strategy:
@@ -65,6 +67,8 @@ jobs:
         run: ./packpack/packpack
 
       - name: Deploy packages
+        # We need this step to run only on push with tag.
+        if: ${{ github.event_name == 'push' && startsWith(github.ref, 'refs/tags/') }}
         env:
           RWS_URL_PART: https://rws.tarantool.org/tarantool-modules
           RWS_AUTH: ${{ secrets.RWS_AUTH }}