git: allow for creating inclusive gitignore files

src/DataTransferObject/ConfigDto.php

@@ -116,6 +116,10 @@ final class ConfigDto
                 new Assert\Type('bool'),
             ]),
 
+            'createInclusiveGitIgnoreFile' => new Assert\Optional([
+                new Assert\Type('bool'),
+            ]),
+
             'createTmuxStartupFile' => new Assert\Optional([
                 new Assert\Type('bool'),
             ]),

templates/drupal/.gitignore.twig

@@ -1,5 +1,6 @@
 # {{ managedText|raw }}
 
+{% if not experimental.createInclusiveGitIgnoreFile %}
 .editorconfig
 .env
 .gitattributes
@@ -44,7 +45,19 @@ docker-compose.override.yaml
 {% if flake is defined %}
 .dir-env/
 {% endif %}
+{% else %}
+# Ignore everything.
+*
 
-{% for path in git.ignore %}
+# Include these things:
+!/{{ drupal.docroot }}/*/custom/**
+{% endif %}
+
+{% for path in git.ignore|sort %}
 {{ path }}
 {% endfor %}
+
+{% if experimental.createInclusiveGitIgnoreFile %}
+# Even if they are in sub-directories.
+!*/
+{% endif %}