refactor: move herokuish app cache from the filesystem into a docker volume

This simplifies cache referencing and also paves the way for removing more from the app git directory.

Refs #1558

tests/unit/build-env.bats

@@ -59,12 +59,16 @@ teardown() {
 }
 
 @test "(build-env) buildpack deploy with Dockerfile" {
-  run /bin/bash -c "dokku config:set --no-restart $TEST_APP BUILDPACK_URL='https://github.com/heroku/heroku-buildpack-nodejs'"
+  run /bin/bash -c "dokku config:set --no-restart $TEST_APP BUILDPACK_URL='https://github.com/dokku/heroku-buildpack-null'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app python dokku@dokku.me:$TEST_APP move_dockerfile_into_place
   echo "output: $output"
   echo "status: $status"
   assert_success
 
-  deploy_app dockerfile
   run /bin/bash -c "dokku --quiet config:get $TEST_APP DOKKU_APP_TYPE"
   echo "output: $output"
   echo "status: $status"

tests/unit/repo.bats

@@ -4,9 +4,11 @@ load test_helper
 
 setup() {
   global_setup
+  create_app
 }
 
 teardown() {
+  destroy_app
   global_teardown
 }
 
@@ -24,7 +26,7 @@ teardown() {
   assert_output "$help_output"
 }
 
-@test "(repo) repo:gc, repo:purge-cache" {
+@test "(repo) repo:gc" {
   run deploy_app
   echo "output: $output"
   echo "status: $status"
@@ -34,29 +36,36 @@ teardown() {
   echo "output: $output"
   echo "status: $status"
   assert_success
+}
 
-  run /bin/bash -c "touch $DOKKU_ROOT/$TEST_APP/cache/derp"
+@test "(repo) repo:purge-cache" {
+  run deploy_app
   echo "output: $output"
   echo "status: $status"
   assert_success
 
-  run /bin/bash -c "find $DOKKU_ROOT/$TEST_APP/cache -type f | wc -l"
+  run /bin/bash -c "docker volume ls -q --filter label=com.dokku.app-name=$TEST_APP | wc -l"
   echo "count: '$output'"
   echo "status: $status"
-  assert_not_output 0
-
-  run /bin/bash -c "dokku repo:purge-cache $TEST_APP"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
+  assert_output 1
 
   run /bin/bash -c "find $DOKKU_ROOT/$TEST_APP/cache -type f | wc -l"
   echo "count: '$output'"
   echo "status: $status"
   assert_output 0
 
-  run destroy_app
+  run /bin/bash -c "dokku repo:purge-cache $TEST_APP"
   echo "output: $output"
   echo "status: $status"
   assert_success
+
+  run /bin/bash -c "docker volume ls -q --filter label=com.dokku.app-name=$TEST_APP | wc -l"
+  echo "count: '$output'"
+  echo "status: $status"
+  assert_output 0
+
+  run /bin/bash -c "find $DOKKU_ROOT/$TEST_APP/cache -type f | wc -l"
+  echo "count: '$output'"
+  echo "status: $status"
+  assert_output 0
 }

tests/unit/test_helper.bash

@@ -535,6 +535,13 @@ add_postdeploy_command() {
   echo "${contents}" >"$APP_REPO_DIR/app.json"
 }
 
+move_dockerfile_into_place() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  mv "$APP_REPO_DIR/alt.Dockerfile" "$APP_REPO_DIR/Dockerfile"
+}
+
 add_requirements_txt() {
   local APP="$1"
   local APP_REPO_DIR="$2"