CI: run tests, build Docker images on Linux

Docker cannot be used on macOS runners, apparently, due to licensing constraints
between Docker corp. and GitHub corp. Fun. Anyway, we now build the Docker images
on a Linux runner.

Helps #20

Signed-off-by: Stephen Gutekanst <stephen@sourcegraph.com>

Author: Stephen Gutekanst

.github/workflows/ci.yml

@@ -23,6 +23,8 @@ jobs:
           brew uninstall go@1.17
           brew install go@1.18
           task install-frontend-deps
+      - name: Run tests
+        run: task test
       - name: Cross-compile for every OS
         run: task cross-compile
       - name: Record latest release version
@@ -39,15 +41,3 @@ jobs:
         env:
           RELEASE_COMMIT: ${{steps.recorded_release_version.outputs.commit}}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      - name: Publish Docker image
-        if: success() && github.ref == 'refs/heads/main' && github.event_Name == 'push' && github.repository == 'sourcegraph/doctree'
-        run: |
-          brew install --cask docker
-          echo "$DOCKER_PASSWORD" | docker login -u="$DOCKER_USERNAME" --password-stdin
-          task build-image
-          docker tag "sourcegraph/doctree:dev" "sourcegraph/doctree:$RELEASE_COMMIT"
-          docker push "sourcegraph/doctree:$RELEASE_COMMIT"
-        env:
-          RELEASE_COMMIT: ${{steps.recorded_release_version.outputs.commit}}
-          DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
-          DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}

.github/workflows/docker.yml

@@ -0,0 +1,32 @@
+name: Docker images
+on:
+  workflow_run:
+    workflows: ["CI"]
+    types:
+      - completed
+jobs:
+  main:
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: "1.18"
+      - name: Install Task
+        uses: arduino/setup-task@v1
+      - name: Build Docker image
+        run: |
+          task install-frontend-deps
+          task build-image
+      - name: Publish Docker image
+        if: success() && github.ref == 'refs/heads/main' && github.event_Name == 'push' && github.repository == 'sourcegraph/doctree'
+        run: |
+          echo "$DOCKER_PASSWORD" | docker login -u="$DOCKER_USERNAME" --password-stdin
+          docker tag "sourcegraph/doctree:dev" "sourcegraph/doctree:$RELEASE_COMMIT"
+          docker push "sourcegraph/doctree:$RELEASE_COMMIT"
+        env:
+          RELEASE_COMMIT: ${{steps.recorded_release_version.outputs.commit}}
+          DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
+          DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}