refactor: Update devcontainer image name construction in build-devcon…

…tainer.yml

.github/shared/devcontainer-image-name.yaml

@@ -0,0 +1,16 @@
+name: "devcontainer image name"
+description: |
+  set up environment variable IMAGE_NAME containing the computed dev container image.
+  the dev container image name is constructed from the repository owner/name and the branch name all lowercased.
+  example : ghcr.io/IONOS-Wordpress/ionos-wordpress-develop-devcontainer for develop branch
+
+runs:
+  using: "composite"
+  steps:
+    - name: build image name
+      run: |
+        # construct IMAGE_NAME from repo owner/name and branch
+        # example value : "ghcr.io/IONOS-Wordpress/ionos-wordpress-develop-devcontainer"
+        IMAGE_NAME="ghcr.io/${GITHUB_REPOSITORY}-${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}-devcontainer"
+        # convert imagename to lowercase and store as environment variable
+        echo "IMAGE_NAME=${IMAGE_NAME@L}" >> "${GITHUB_ENV}"

.github/workflows/build-devcontainer.yml

@@ -1,4 +1,5 @@
 name: 'build devcontainer image'
+
 on:
   # rebuild any PRs and main branch changes
   pull_request:
@@ -29,13 +30,7 @@ jobs:
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: build image name
-        run: |
-          # construct IMAGE_NAME from repo owner/name and branch
-          # example value : "ghcr.io/IONOS-Wordpress/ionos-wordpress-develop-devcontainer"
-          IMAGE_NAME="ghcr.io/${GITHUB_REPOSITORY}-${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}-devcontainer"
-          # convert imagename to lowercase and store as environment variable
-          echo "IMAGE_NAME=${IMAGE_NAME@L}" >> "${GITHUB_ENV}"
+      - uses: "./.github/shared/devcontainer-image-name.yaml"
 
       - name: Pre-build image and run make ci-build in dev container
         uses: devcontainers/ci@v0.3
@@ -46,7 +41,7 @@ jobs:
           # "push" is already the default
           # eventFilterForPush: push
 
-          # name of the pushed image (example : "ghcr.io/wordpress-ionos/wordpress-ionos-devcontainer")
+          # use the IMAGE_NAME environment variable produced by ./.github/shared/devcontainer-image-name.yaml
           imageName: ${{ env.IMAGE_NAME }}
 
           # make some tests to test the devcontainer image is working