Also build the Docker image on PRs, but only push it on pushes (llvm#78)

Author: ldionne

.github/workflows/build.yaml renamed to .github/workflows/build-docker.yaml

@@ -3,6 +3,8 @@ name: Build Docker image
 on:
   push:
     branches: ['main']
+  pull_request:
+    branches: ['main']
 
 permissions:
   contents: read
@@ -16,15 +18,17 @@ jobs:
 
     steps:
     - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
+
     - name: Log in to the Container registry
       uses: docker/login-action@5e57cd118135c172c3672efd75eb46360885c0ef
       with:
         registry: ghcr.io
         username: ${{ github.actor }}
         password: ${{ secrets.GITHUB_TOKEN }}
+
     - name: Build and push Docker image
       id: push
       uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83
       with:
-        push: true
+        push: ${{ github.event_name == 'push' }}
         tags: ghcr.io/${{github.repository}}:latest

Dockerfile

@@ -6,7 +6,7 @@ RUN apk update \
 
 WORKDIR /var/src/lnt
 
-COPY requirements.server.txt setup.py .
+COPY requirements*.txt setup.py .
 # setup.py uses lnt.__version__ etc.
 COPY lnt/__init__.py lnt/__init__.py
 # we build the cperf extension during install