feat(ci): run upgrade tests for multiple "old" versions

Currently only 2.8.0 is used to run migration tests, all the way up to
the "new" (current) version. This means that only features that are
shared across all versions from "old" to "new" can be tested, e.g. a
plugin that is not available in `2.8.0` cannot be configured and used
in migration tests.

This commit introduces a list of "old_versions" and repeats the tests
for each. Tests can use the `OLD_KONG_VERSION` environment variable to
determine whether they should execute for the current version.

scripts/upgrade-tests/source-versions

@@ -0,0 +1,2 @@
+2.8.0
+3.4.0

scripts/upgrade-tests/test-upgrade-path.sh

@@ -23,19 +23,6 @@ set -e
 
 trap "echo exiting because of error" 0
 
-function get_current_version() {
-    local image_tag=$1
-    local version_from_rockspec=$(perl -ne 'print "$1\n" if (/^\s*tag = "(.*)"/)' kong*.rockspec)
-    if docker pull $image_tag:$version_from_rockspec >/dev/null 2>/dev/null
-    then
-        echo $version_from_rockspec-ubuntu
-    else
-        echo master-ubuntu
-    fi
-}
-
-export OLD_KONG_VERSION=2.8.0
-export OLD_KONG_IMAGE=kong:$OLD_KONG_VERSION-ubuntu
 export KONG_PG_HOST=localhost
 export KONG_TEST_PG_HOST=localhost
 
@@ -91,13 +78,19 @@ function prepare_container() {
 }
 
 function build_containers() {
+    # Kong version >= 3.3 moved non Bazel-built dev setup to make dev-legacy
+    if (( $(echo "$OLD_KONG_VERSION" | sed 's/\.//g') >= 330 )); then
+        old_make_target="dev-legacy"
+    else
+        old_make_target="dev"
+    fi
+
     echo "Building containers"
 
     [ -d worktree/$OLD_KONG_VERSION ] || git worktree add worktree/$OLD_KONG_VERSION $OLD_KONG_VERSION
     $COMPOSE up --wait
     prepare_container $OLD_CONTAINER
-    docker exec -w /kong $OLD_CONTAINER make dev CRYPTO_DIR=/usr/local/kong
-    # Kong version >= 3.3 moved non Bazel-built dev setup to make dev-legacy
+    docker exec -w /kong $OLD_CONTAINER make $old_make_target CRYPTO_DIR=/usr/local/kong
     make dev-legacy CRYPTO_DIR=/usr/local/kong
 }
 
@@ -155,7 +148,7 @@ function initialize_test_list() {
 
 function run_tests() {
     # Run the tests
-    BUSTED_ENV="env KONG_DATABASE=$1 KONG_DNS_RESOLVER= KONG_TEST_PG_DATABASE=kong" 
+    BUSTED_ENV="env KONG_DATABASE=$1 KONG_DNS_RESOLVER= KONG_TEST_PG_DATABASE=kong OLD_KONG_VERSION=$OLD_KONG_VERSION"
 
     shift
 
@@ -186,15 +179,29 @@ function run_tests() {
 }
 
 function cleanup() {
-    git worktree remove worktree/$OLD_KONG_VERSION --force
+    sudo git worktree remove worktree/$OLD_KONG_VERSION --force
     $COMPOSE down
-    deactivate
 }
 
+
 source $venv_script
-build_containers
-initialize_test_list
-run_tests postgres
-[ -z "$UPGRADE_ENV_PREFIX" ] && cleanup
+
+# Load supported "old" versions to run migration tests against
+old_versions=()
+mapfile -t old_versions < "scripts/upgrade-tests/source-versions"
+
+for old_version in "${old_versions[@]}"; do
+    export OLD_KONG_VERSION=$old_version
+    export OLD_KONG_IMAGE=kong:$OLD_KONG_VERSION-ubuntu
+
+    echo "Running tests using $OLD_KONG_VERSION as \"old version\" of Kong"
+
+    build_containers
+    initialize_test_list
+    run_tests postgres
+    [ -z "$UPGRADE_ENV_PREFIX" ] && cleanup
+done
+
+deactivate
 
 trap "" 0

spec/05-migration/plugins/http-log/migrations/001_280_to_300_spec.lua

@@ -8,7 +8,10 @@ local uh = require "spec.upgrade_helpers"
 -- to test the migration process. do not change it to use dynamic port.
 local HTTP_PORT = 29100
 
-describe("http-log plugin migration", function()
+local OLD_KONG_VERSION = os.getenv("OLD_KONG_VERSION")
+local handler = OLD_KONG_VERSION:sub(1,3) == "2.8" and describe or pending
+
+handler("http-log plugin migration", function()
     local mock
     lazy_setup(function()
       assert(uh.start_kong())

spec/05-migration/plugins/post-function/migrations/001_280_to_300_spec.lua

@@ -1,7 +1,12 @@
 
 local uh = require "spec/upgrade_helpers"
 
-describe("post-function plugin migration", function()
+
+local OLD_KONG_VERSION = os.getenv("OLD_KONG_VERSION")
+local handler = OLD_KONG_VERSION:sub(1,3) == "2.8" and describe or pending
+
+
+handler("post-function plugin migration", function()
 
     lazy_setup(function()
       assert(uh.start_kong())

spec/05-migration/plugins/pre-function/migrations/001_280_to_300_spec.lua

@@ -1,7 +1,10 @@
 
 local uh = require "spec/upgrade_helpers"
 
-describe("pre-function plugin migration", function()
+local OLD_KONG_VERSION = os.getenv("OLD_KONG_VERSION")
+local handler = OLD_KONG_VERSION:sub(1,3) == "2.8" and describe or pending
+
+handler("pre-function plugin migration", function()
 
     lazy_setup(function()
       assert(uh.start_kong())