fix: Improve workflow for main branch and PRs (#17)

This makes it so that the main branch will push images but PRs won't.
This also puts integration tests back in the `+all` target.

.github/workflows/build.yml

@@ -1,9 +1,7 @@
-name: Earthly +build
+name: Earthly main branch +build
 
 on:
   workflow_dispatch:
-  merge_group:
-  pull_request:
   push:
     branches:
       - main
@@ -15,17 +13,19 @@ jobs:
   build:
     permissions:
       packages: write
-    timeout-minutes: 30
+    timeout-minutes: 60
     runs-on: ubuntu-latest
 
     steps:
       - uses: earthly/actions-setup@v1
         with:
           use-cache: true
-          version: v0.8.0
+          version: v0.8.2
 
       # Setup repo and add caching
       - uses: actions/checkout@v4
+        with:
+          ref: main
 
       - name: Login to GitHub Container Registry
         uses: docker/login-action@v3
@@ -35,4 +35,4 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Run build
-        run: earthly --push --ci -P +all
+        run: earthly --push --ci -P +build