Convert repository name to lowercase

Author: bthomee

.github/workflows/ubuntu.yml

@@ -31,7 +31,11 @@ jobs:
           --build-arg GCC_VERSION=${{ matrix.version.gcc }} \
           --tag ${DOCKER_REGISTRY}/${{ github.repository }}/${{ matrix.version.os }}:gcc${{ matrix.version.gcc }}
       - name: Push the Docker image
-        run: docker push ${DOCKER_REGISTRY}/${{ github.repository }}/${{ matrix.version.os }}:gcc${{ matrix.version.gcc }}
+        run: |
+          # Convert the repository name to lowercase as the organization name is
+          # uppercase, which is not permitted by the Docker registry.
+          DOCKER_REPOSITORY=${GITHUB_REPOSITORY,,}
+          docker push ${DOCKER_REGISTRY}/${DOCKER_REPOSITORY}/${{ github.repository }}/${{ matrix.version.os }}:gcc${{ matrix.version.gcc }}
 
   # Build the Docker image for Ubuntu using different versions of Clang.
   clang:
@@ -57,4 +61,8 @@ jobs:
           --build-arg CLANG_VERSION=${{ matrix.version.clang }} \
           --tag ${DOCKER_REGISTRY}/${{ github.repository }}/${{ matrix.version.os }}:clang${{ matrix.version.clang }}
       - name: Push the Docker image
-        run: docker push ${DOCKER_REGISTRY}/${{ github.repository }}/${{ matrix.version.os }}:clang${{ matrix.version.clang }}
+        run: |
+          # Convert the repository name to lowercase as the organization name is
+          # uppercase, which is not permitted by the Docker registry.
+          DOCKER_REPOSITORY=${GITHUB_REPOSITORY,,}
+          docker push ${DOCKER_REGISTRY}/${DOCKER_REPOSITORY}/${{ matrix.version.os }}:clang${{ matrix.version.clang }}