MM-68120 - Use repo checkout for build files in server-ci-artifacts (#35842)

* Use repo checkout for Dockerfile in server-ci-artifacts build-docker job

The build-docker job was downloading server-build-artifact to get the
Dockerfile and supporting files for every PR. Switch to checking out
server/build/ directly from the repo for external PRs, while keeping
the artifact-based flow for same-repo PRs so that Dockerfile changes
can be tested before merge.

Only upload server-build-artifact when the PR comes from the same repo,
since external PRs no longer use it.

Made-with: Cursor

* retrigger pipelines

* undo previous commit

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

.github/workflows/server-ci-artifacts.yml

@@ -82,12 +82,15 @@ jobs:
           username: mattermostdev
           password: ${{ secrets.DOCKERHUB_DEV_TOKEN }}
 
-      - name: cd/setup-cosign
-        uses: sigstore/cosign-installer@faadad0cce49287aee09b3a48701e75088a2c6ad # v4.0.0
+      - name: cd/checkout-build-files
+        if: github.event.workflow_run.head_repository.full_name != github.repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
-          cosign-release: v${{ env.COSIGN_VERSION }}
+          sparse-checkout: server/build/
+          sparse-checkout-cone-mode: true
 
-      - name: cd/download-artifacts-from-PR-workflow
+      - name: cd/download-build-artifact
+        if: github.event.workflow_run.head_repository.full_name == github.repository
         uses: actions/download-artifact@70fc10c6e5e1ce46ad2ea6f2b72d43f7d47b13c3 # v8.0.0
         with:
           run-id: ${{ github.event.workflow_run.id }}
@@ -95,6 +98,11 @@ jobs:
           name: server-build-artifact
           path: server/build/
 
+      - name: cd/setup-cosign
+        uses: sigstore/cosign-installer@faadad0cce49287aee09b3a48701e75088a2c6ad # v4.0.0
+        with:
+          cosign-release: v${{ env.COSIGN_VERSION }}
+
       - name: cd/setup-docker-buildx
         uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 

.github/workflows/server-ci.yml

@@ -385,6 +385,7 @@ jobs:
           compression-level: 0
           retention-days: 2
       - name: Persist build artifacts
+        if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository
         uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
         with:
           name: server-build-artifact