docs: document robots.txt

# Conflicts:
#	admin/search-engines-indexation.md

admin/index.md

@@ -16,3 +16,4 @@ These documents are targeted to people who run Forgejo on their machines.
 - [Incoming Email](incoming-email)
 - [Logging Configuration](logging-documentation)
 - [Actions](actions)
+- [Search Engines and robots.txt](search-engines-indexation)

admin/search-engines-indexation.md

@@ -0,0 +1,43 @@
+---
+layout: '~/layouts/Markdown.astro'
+title: 'Search Engines Indexation'
+license: 'Apache-2.0'
+origin_url: 'https://github.com/go-gitea/gitea/blob/62ac3251fa545d32bdfc9ff824106b97ec63edbb/docs/content/doc/administration/search-engines-indexation.en-us.md'
+---
+
+# Search engines indexation of your Forgejo installation
+
+By default your Forgejo installation will be indexed by search engines.
+If you don't want your repository to be visible for search engines read further.
+
+## Block search engines indexation using robots.txt
+
+To make Forgejo serve a custom `robots.txt` (default: empty 404) for top level installations,
+create a file called `robots.txt` at the root of the `CustomPath` as displayed in the `/admin` page.
+
+Examples on how to configure the `robots.txt` can be found at [https://moz.com/learn/seo/robotstxt](https://moz.com/learn/seo/robotstxt).
+
+```txt
+User-agent: *
+Disallow: /
+```
+
+If you installed Forgejo in a subdirectory, you will need to create or edit the `robots.txt` in the top level directory.
+
+```txt
+User-agent: *
+Disallow: /forgejo/
+```
+
+## Disallow crawling archives to save disk space
+
+If the archive files are crawled, they will be generated dynamically
+and kept around which can amount to a lot of disk. To prevent that
+from happening, add the following to the `robots.txt` file:
+
+```txt
+User-agent: *
+Disallow: /*/*/archive/
+```
+
+See also a more complete example [at Codeberg](https://codeberg.org/robots.txt).