fix: isolate preview deploys into separate directories

Give each preview its own clone at /opt/apps/{APP_NAME}-pr-{N}
instead of sharing /opt/apps/{APP_NAME} with production. This
eliminates the race condition where concurrent preview and
production deploys could build from the wrong code.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: baijum

.github/workflows/preview.yml

@@ -25,26 +25,33 @@ jobs:
             APP_DB=$(echo "${APP_NAME}" | tr '-' '_')_db
             SCHEMA_NAME="pr_${PR_NUMBER}"
 
-            cd /opt/apps/${APP_NAME}
-
-            # Fetch and checkout the PR branch
-            git fetch origin pull/${PR_NUMBER}/head:pr-${PR_NUMBER} --force
-            git checkout pr-${PR_NUMBER}
+            PREVIEW_DIR="/opt/apps/${APP_NAME}-pr-${PR_NUMBER}"
+
+            # Clone the repo into a dedicated preview directory (or pull if it exists)
+            if [ -d "${PREVIEW_DIR}" ]; then
+              cd "${PREVIEW_DIR}"
+              git fetch origin pull/${PR_NUMBER}/head:pr-${PR_NUMBER} --force
+              git checkout pr-${PR_NUMBER}
+            else
+              git clone /opt/apps/${APP_NAME} "${PREVIEW_DIR}"
+              cd "${PREVIEW_DIR}"
+              git fetch origin pull/${PR_NUMBER}/head:pr-${PR_NUMBER} --force
+              git checkout pr-${PR_NUMBER}
+            fi
 
             # Create preview schema in the app's database
             docker compose -f /opt/platform/docker-compose.yml exec -T postgres \
               psql -U postgres -d ${APP_DB} -c "CREATE SCHEMA IF NOT EXISTS ${SCHEMA_NAME}"
 
-            # Read the app's .env and generate a preview-specific version
-            # with DATABASE_URL pointing to the PR schema
-            if [ ! -f deploy/.env ]; then
-              echo "ERROR: deploy/.env not found. Create it from deploy/env.template first."
+            # Copy production .env as base for preview config
+            if [ ! -f /opt/apps/${APP_NAME}/deploy/.env ]; then
+              echo "ERROR: /opt/apps/${APP_NAME}/deploy/.env not found. Deploy production first."
               exit 1
             fi
 
             # Generate preview .env with schema-aware DATABASE_URL
             sed "s|^DATABASE_URL=.*|DATABASE_URL=postgresql://postgres:$(grep POSTGRES_PASSWORD /opt/platform/.env | cut -d= -f2)@postgres:5432/${APP_DB}?options=-csearch_path%3D${SCHEMA_NAME}|" \
-              deploy/.env > deploy/.env.pr-${PR_NUMBER}
+              /opt/apps/${APP_NAME}/deploy/.env > deploy/.env.pr-${PR_NUMBER}
 
             # Build and start the app container (skip optional services like celery-worker)
             docker compose -p ${APP_NAME}-pr-${PR_NUMBER} -f deploy/docker-compose.yml \
@@ -65,9 +72,6 @@ jobs:
             docker compose -f /opt/platform/docker-compose.yml exec -T caddy \
               caddy reload --config /etc/caddy/Caddyfile
 
-            # Switch back to main so production deploys aren't affected
-            git checkout main
-
       - name: Post preview URL
         uses: actions/github-script@v7
         with:
@@ -113,9 +117,13 @@ jobs:
             APP_DB=$(echo "${APP_NAME}" | tr '-' '_')_db
             SCHEMA_NAME="pr_${PR_NUMBER}"
 
+            PREVIEW_DIR="/opt/apps/${APP_NAME}-pr-${PR_NUMBER}"
+
             # Stop and remove preview containers
-            cd /opt/apps/${APP_NAME}
-            docker compose -p ${APP_NAME}-pr-${PR_NUMBER} -f deploy/docker-compose.yml down --rmi local || true
+            if [ -d "${PREVIEW_DIR}" ]; then
+              cd "${PREVIEW_DIR}"
+              docker compose -p ${APP_NAME}-pr-${PR_NUMBER} -f deploy/docker-compose.yml down --rmi local || true
+            fi
 
             # Drop the preview schema
             docker compose -f /opt/platform/docker-compose.yml exec -T postgres \
@@ -128,6 +136,5 @@ jobs:
             docker compose -f /opt/platform/docker-compose.yml exec -T caddy \
               caddy reload --config /etc/caddy/Caddyfile
 
-            # Clean up preview .env and branch
-            rm -f deploy/.env.pr-${PR_NUMBER}
-            git branch -D pr-${PR_NUMBER} || true
+            # Remove the preview directory entirely
+            rm -rf "${PREVIEW_DIR}"