comments to remind future me of how this all works

bin/compile

@@ -493,6 +493,7 @@ unset COMPOSER_bak
 
 # clean up
 rm -rf /app/.heroku/php-min $build_dir/.heroku/php-min
+# unset composer function that used php-min for invocation
 unset -f composer
 
 # export our "do not auto.start APM extensions" magic INI directory to PHP_INI_SCAN_DIR for ourself and for later buildpacks (but not for runtime)
@@ -502,6 +503,7 @@ echo "export PHP_INI_SCAN_DIR=\${PHP_INI_SCAN_DIR-}:$bp_dir/conf/php/apm-nostart
 # earlier we wrote at least one $PATH entry that we'll need now (and just above we added a PHP_INI_SCAN_DIR export), and installed packages will likely have added to it too
 source $bp_dir/export
 
+# from here onwards we're using composer with the PHP runtime that we installed
 composer() {
 	$engine $(which composer) "$@"
 }