Fix problem with DEBUG variable (#435)

* Fix problem with DEBUG variable

* Add condition for starting ci on pull requests

* Add default value

* Add default value in another place

* Fix error in bash statement

* Replace && on if condition

.github/workflows/blank.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
     tags:
+  pull_request:
 
 jobs:
   build:
@@ -14,12 +15,21 @@ jobs:
       run: docker version
     - name: Debug if needed
       run: |
-        [[ "$DEBUG" ]] && env
+        export DEBUG=${DEBUG:-false}
+
+        if [[ "$DEBUG" == "true" ]]; then
+          env
+        fi
       env:
         DEBUG: ${{secrets.DEBUG}}
     - name: Build image
       run: |
         export GIT_BRANCH="${GITHUB_REF/refs\/heads\//}"
+        export GIT_TAG="${GITHUB_REF/refs\/tags\//}"
+
+        if [[ "$GIT_TAG" != "$GITHUB_REF" ]]; then
+          export GIT_BRANCH=$GIT_TAG
+        fi
 
         docker build \
         --build-arg CI="$GITHUB_WORKFLOW" \