feat: allow customizing the various nginx templates

This will let custom distributions of Dokku to override the internal templates without needing to repackage Dokku or overwrite core files.

docs/development/plugin-triggers.md

@@ -854,6 +854,36 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+### `nginx-app-template-source`
+
+- Description: Return the path to a `sigil` template that should be used to generate a given nginx configuration file.
+- Invoked by: `nginx-vhosts#build-config`
+- Arguments: `$APP $TEMPLATE_TYPE`
+  - The `TEMPLATE_TYPE` argument can be one of: `[app-config, hsts-config, validate-config]`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+
+APP="$1"
+TEMPLATE_TYPE="$2"
+case "$TEMPLATE_TYPE" in
+  app-config)
+    echo "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/app.conf.sigil";;
+  hsts-config)
+    echo "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/hsts.conf.sigil";;
+  validate-config)
+    echo "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/validate.conf.sigil";;
+  *)
+    dokku_log_fail "Invalid template type: ${TEMPLATE_TYPE}"
+esac
+```
+
+The default templates are viewable here: [plugins/nginx-vhosts/templates/](https://github.com/dokku/dokku/tree/master/plugins/nginx-vhosts/templates)
+
 ### `nginx-dokku-template-source`
 
 - Description: Return the path to a `sigil` template that should be used to generate the `dokku.conf` nginx configuration file.

plugins/20_events/nginx-app-template-source

@@ -0,0 +1 @@
+hook

plugins/nginx-vhosts/functions

@@ -315,21 +315,23 @@ is_grpc_enabled() {
 
 nginx_build_config() {
   declare desc="build nginx config to proxy app containers using sigil"
-  local APP="$1"
+  declare APP="$1" DOKKU_APP_LISTEN_PORT="$2" DOKKU_APP_LISTEN_IP="$3"
   verify_app_name "$APP"
-  local DOKKU_APP_LISTEN_PORT="$2"
-  local DOKKU_APP_LISTEN_IP="$3"
   local VHOST_PATH="$DOKKU_ROOT/$APP/VHOST"
   local APP_URLS_PATH="$DOKKU_ROOT/$APP/URLS"
   local NGINX_TEMPLATE_NAME="nginx.conf.sigil"
-  local DEFAULT_NGINX_TEMPLATE="$PLUGIN_AVAILABLE_PATH/nginx-vhosts/templates/$NGINX_TEMPLATE_NAME"
-  local NGINX_TEMPLATE="$DEFAULT_NGINX_TEMPLATE"
+  local NGINX_TEMPLATE="$PLUGIN_AVAILABLE_PATH/nginx-vhosts/templates/$NGINX_TEMPLATE_NAME"
   local SCHEME=http
   local NGINX_TEMPLATE_SOURCE="built-in"
   local APP_SSL_PATH="$DOKKU_ROOT/$APP/tls"
   local RAW_TCP_PORTS="$(get_app_raw_tcp_ports "$APP")"
   local DOKKU_APP_LISTENERS
 
+  CUSTOM_NGINX_TEMPLATE="$(plugn trigger nginx-app-template-source "$APP" "app-config")"
+  if [[ -n "$CUSTOM_NGINX_TEMPLATE" ]]; then
+    NGINX_TEMPLATE="$CUSTOM_NGINX_TEMPLATE"
+  fi
+
   local IS_APP_VHOST_ENABLED=true
   plugn trigger domains-vhost-enabled "$APP" || IS_APP_VHOST_ENABLED=false
 

plugins/nginx-vhosts/internal-functions

@@ -22,6 +22,11 @@ fn-nginx-vhosts-manage-hsts() {
   local NGINX_HSTS_CONF="$DOKKU_ROOT/$APP/nginx.conf.d/hsts.conf"
   local HSTS_TEMPLATE="$PLUGIN_AVAILABLE_PATH/nginx-vhosts/templates/hsts.conf.sigil"
 
+  CUSTOM_HSTS_TEMPLATE="$(plugn trigger nginx-app-template-source "$APP" "hsts-config")"
+  if [[ -n "$CUSTOM_HSTS_TEMPLATE" ]]; then
+    HSTS_TEMPLATE="$CUSTOM_HSTS_TEMPLATE"
+  fi
+
   if [[ "$HSTS" == "false" ]] || [[ "$SSL_ENABLED" != "true" ]]; then
     rm -rf "$NGINX_HSTS_CONF"
     return
@@ -137,6 +142,11 @@ nginx_vhosts_is_valid_nginx_config_func() {
   local TMP_OUTPUT=$(mktemp "/tmp/dokku-${DOKKU_PID}-${FUNCNAME[0]}.XXXXXX")
   trap "rm -rf '$TMP_OUTPUT' >/dev/null" RETURN INT TERM EXIT
 
+  CUSTOM_VALIDATE_TEMPLATE="$(plugn trigger nginx-app-template-source "$APP" "validate-config")"
+  if [[ -n "$CUSTOM_VALIDATE_TEMPLATE" ]]; then
+    VALIDATE_TEMPLATE="$CUSTOM_VALIDATE_TEMPLATE"
+  fi
+
   sigil -f "$VALIDATE_TEMPLATE" NGINX_CONF="$DOKKU_ROOT/$APP/nginx.conf" | cat -s >"$TMP_OUTPUT"
   sudo "$NGINX_LOCATION" -t -c "$TMP_OUTPUT" 2>/dev/null
 }