Redirects in GitLab documentation

When you move, rename, or delete a page, you must add a redirect. Redirects reduce how often users get 404s when visiting the documentation site from out-of-date links, like:

Bookmarks
Links from external sites
Links from old blog posts
Links in the documentation site global navigation

Add a redirect to ensure:

Users see the new page and can update or delete their bookmark.
External sites can update their links, especially sites that have automation that checks for redirected links.
The documentation site global navigation does not link to a missing page.

The links in the global navigation are already tested in the gitlab-docs project. If the redirect is missing, the gitlab-docs project's main branch might break.

Be sure to assign a technical writer to any merge request that moves, renames, or deletes a page. Technical Writers can help with any questions and can review your change.

There are two types of redirects:

Redirect added into the documentation files themselves, for users who view the docs in /help on self-managed instances. For example, /help on GitLab.com. These must be added in the same MR that renames or moves a doc. Redirects to internal pages expire after three months and redirects to external pages (starting with https:) expire after a year.
GitLab Pages redirects, which are added automatically after redirect files expire. They must not be manually added by contributors and expire after nine months. Redirects pointing to external sites are not added to the GitLab Pages redirects.

Expired redirect files are removed from the documentation projects by the clean_redirects Rake task, as part of the Technical Writing team's monthly tasks.

Add a redirect

NOTE: If the renamed page is new, you can sometimes skip the following steps and ask a Technical Writer to manually add the redirect to redirects.yaml. For example, if you add a new page and then rename it before it's added to a release on the 18th. The old page is not in any version's /help section, so a technical writer can jump straight to the Pages redirect.

To add a redirect:

In the repository (gitlab, gitlab-runner, omnibus-gitlab, or charts), create a new documentation file. Don't delete the old one. The easiest way is to copy it. For example:
```
cp doc/user/search/old_file.md doc/api/new_file.md
```

Add the redirect code to the old documentation file by running the following Rake task. The first argument is the path of the old file, and the second argument is the path of the new file:

To redirect to a page in the same project, use relative paths and the .md extension. Both old and new paths start from the same location. In the following example, both paths are relative to doc/:
```
bundle exec rake "gitlab:docs:redirect[doc/user/search/old_file.md, doc/api/new_file.md]"
```

To redirect to a page in a different project or site, use the full URL (with https://) :

bundle exec rake "gitlab:docs:redirect[doc/user/search/old_file.md, https://example.com]"

Alternatively, you can omit the arguments and be prompted to enter the values:
```
bundle exec rake gitlab:docs:redirect
```

If you don't want to use the Rake task, you can use the following template:

---
redirect_to: '../newpath/to/file/index.md'
remove_date: 'YYYY-MM-DD'
---

This document was moved to [another location](../path/to/file/index.md).

<!-- This redirect file can be deleted after <YYYY-MM-DD>. -->
<!-- Redirects that point to other docs in the same project expire in three months. -->
<!-- Redirects that point to docs in a different project or site (for example, link is not relative and starts with `https:`) expire in one year. -->
<!-- Before deletion, see: https://docs.gitlab.com/ee/development/documentation/redirects.html -->

Replace both instances of ../newpath/to/file/index.md with the new file path.
Replace YYYY-MM-DD with the expiry date, as explained in the template.

If the documentation page being moved has any Disqus comments, follow the steps described in Redirections for pages with Disqus comments.
Open a merge request with your changes. If a documentation page you're removing includes images that aren't used with any other documentation pages, be sure to use your merge request to delete those images from the repository.
Assign the merge request to a technical writer for review and merge.
Search for links to the old documentation file. You must find and update all links that point to the old documentation file:
- In https://gitlab.com/gitlab-com/www-gitlab-com, search for full URLs: grep -r "docs.gitlab.com/ee/path/to/file.html" .
- In https://gitlab.com/gitlab-org/gitlab-docs/-/tree/master/content/_data, search the navigation bar configuration files for the path with .html: grep -r "path/to/file.html" .
- In any of the four internal projects, search for links in the docs and codebase. Search for all variations, including full URL and just the path. For example, go to the root directory of the gitlab project and run:
```
grep -r "docs.gitlab.com/ee/path/to/file.html" .
grep -r "path/to/file.html" .
grep -r "path/to/file.md" .
grep -r "path/to/file" .
```
  You may need to try variations of relative links, such as ../path/to/file or ../file to find every case.

Redirections for pages with Disqus comments

If the documentation page being relocated already has Disqus comments, we need to preserve the Disqus thread.

Disqus uses an identifier per page, and for https://docs.gitlab.com, the page identifier is configured to be the page URL. Therefore, when we change the document location, we need to preserve the old URL as the same Disqus identifier.

To do that, add to the front matter the variable disqus_identifier, using the old URL as value. For example, let's say we moved the document available under https://docs.gitlab.com/my-old-location/README.html to a new location, https://docs.gitlab.com/my-new-location/index.html.

Into the new document front matter, we add the following information. You must include the filename in the disqus_identifier URL, even if it's index.html or README.html.

---
disqus_identifier: 'https://docs.gitlab.com/my-old-location/README.html'
---