feat: make heroku-20/focal the default stack for herokuish builds

Closes #4621

Makefile

@@ -14,7 +14,7 @@ PROCFILE_UTIL_URL ?= https://github.com/josegonzalez/go-procfile-util/releases/d
 SIGIL_URL ?= https://github.com/gliderlabs/sigil/releases/download/v${SIGIL_VERSION}/sigil_${SIGIL_VERSION}_Linux_x86_64.tgz
 SSHCOMMAND_URL ?= https://github.com/dokku/sshcommand/releases/download/v${SSHCOMMAND_VERSION}/sshcommand_${SSHCOMMAND_VERSION}_linux_x86_64.tgz
 STACK_URL ?= https://github.com/gliderlabs/herokuish.git
-PREBUILT_STACK_URL ?= gliderlabs/herokuish:latest
+PREBUILT_STACK_URL ?= gliderlabs/herokuish:latest-20
 DOKKU_LIB_ROOT ?= /var/lib/dokku
 PLUGINS_PATH ?= ${DOKKU_LIB_ROOT}/plugins
 CORE_PLUGINS_PATH ?= ${DOKKU_LIB_ROOT}/core-plugins

docs/appendices/0.25.0-migration-guide.md

@@ -16,6 +16,8 @@ The [dokku-registry](https://github.com/dokku/dokku-registry) plugin is now buil
 - The network plugin can now set an `initial-network` for all containers on creation. This is a replacement for specifying the `--network` flag via the `docker-options` plugin. Please see the [network documentation](/docs/networking/network.md#attaching-an-app-to-a-network) for more information.
 - The `dokku run` command now always removes the ephemeral container on exit. Users that need a persistent container should instead specify a `console` process type in their `Procfile` specifying an available shell (usually either `bash` or `sh`) and scale that container appropriately.
 - The `pre-deploy` plugin trigger is now called internally by Dokku. Scheduler plugins should avoid calling this trigger, as any image changes introduced by subsequent trigger calls will be ignored.
+- The default image used for Herokuish Buildpack builds is now `gliderlabs/herokuish:latest-20`, and is based on both the `heroku-20` stack as well as Ubuntu 20.04. Users that wish to stick with the old, `heroku-18`/Ubuntu 18.04 builder may specify `gliderlabs/herokuish:latest-18` as their builder image. Please see the [herokuish buildpack deployment documentation](/docs/deployment/builders/herokuish-buildpacks.md#customizing-the-buildpack-stack-builder) for more information on how to specify a custom buildpack stack builder.
+  - This change does not impact any users of Cloud Native Buildpacks.
 
 ### Deprecations
 

docs/deployment/builders/herokuish-buildpacks.md

@@ -158,7 +158,7 @@ dokku buildpacks:set-property node-js-app stack
 
 A change in the stack builder value will execute the `post-stack-set` trigger.
 
-Finally, stack builders can be set or unset globally as a fallback. This will take precedence over a globally set `DOKKU_IMAGE` environment variable (`gliderlabs/herokuish:latest` by default).
+Finally, stack builders can be set or unset globally as a fallback. This will take precedence over a globally set `DOKKU_IMAGE` environment variable (`gliderlabs/herokuish:latest-20` by default).
 
 ```shell
 # set globally
@@ -179,17 +179,17 @@ dokku buildpacks:report
 ```
 =====> node-js-app buildpacks information
        Buildpacks computed stack:  gliderlabs/herokuish:v0.5.23-20
-       Buildpacks global stack:    gliderlabs/herokuish:latest
+       Buildpacks global stack:    gliderlabs/herokuish:latest-20
        Buildpacks list:            https://github.com/heroku/heroku-buildpack-nodejs.git
        Buildpacks stack:           gliderlabs/herokuish:v0.5.23-20
 =====> python-sample buildpacks information
-       Buildpacks computed stack:  gliderlabs/herokuish:v0.5.23-20
-       Buildpacks global stack:    gliderlabs/herokuish:latest
+       Buildpacks computed stack:  gliderlabs/herokuish:latest-20
+       Buildpacks global stack:    gliderlabs/herokuish:latest-20
        Buildpacks list:            https://github.com/heroku/heroku-buildpack-nodejs.git,https://github.com/heroku/heroku-buildpack-python.git
        Buildpacks stack:
 =====> ruby-sample buildpacks information
-       Buildpacks computed stack:  gliderlabs/herokuish:v0.5.23-20
-       Buildpacks global stack:    gliderlabs/herokuish:latest
+       Buildpacks computed stack:  gliderlabs/herokuish:latest-20
+       Buildpacks global stack:    gliderlabs/herokuish:latest-20
        Buildpacks list:
        Buildpacks stack:
 ```

dokku

@@ -41,7 +41,7 @@ DOKKU_DISTRO=$(
 # configuration can ever override the DOCKER_BIN value
 export DOCKER_BIN=${DOCKER_BIN:="docker"}
 
-export DOKKU_IMAGE=${DOKKU_IMAGE:="gliderlabs/herokuish:latest"}
+export DOKKU_IMAGE=${DOKKU_IMAGE:="gliderlabs/herokuish:latest-20"}
 export DOKKU_CNB_BUILDER=${DOKKU_CNB_BUILDER:="heroku/buildpacks"}
 export DOKKU_LIB_ROOT=${DOKKU_LIB_PATH:="/var/lib/dokku"}
 

tests/apps/dockerfile/app.json

@@ -25,7 +25,7 @@
       "generator": "echo 5"
     }
   },
-  "image": "gliderlabs/herokuish",
+  "image": "gliderlabs/herokuish:latest-20",
   "addons": [
     "dokku-postgres",
     "dokku-redis"

tests/apps/multi/Gemfile

@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-ruby '2.6.2'
+ruby '2.6.8'
 
 gem 'compass', ">= 1.0.1"
 gem 'sass-globbing'

tests/apps/nodejs-express/app.json

@@ -25,7 +25,7 @@
       "generator": "echo 5"
     }
   },
-  "image": "gliderlabs/herokuish",
+  "image": "gliderlabs/herokuish:latest-20",
   "addons": [
     "dokku-postgres",
     "dokku-redis"

tests/apps/ruby/Gemfile

@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
-ruby '2.6.2'
+ruby '2.6.8'
 
 gem 'sinatra', '~>2.1.0'
 gem 'thin'