Docs review: wording, styles, missing links

- Fix "introduced in" note
- Add missing links
- Remove unnecessary hrs
- Wording
- Feature badge (admin only)

doc/administration/index.md

@@ -51,7 +51,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
 - [Third party offers](../user/admin_area/settings/third_party_offers.md)
 - [Compliance](compliance.md): A collection of features from across the application that you may configure to help ensure that your GitLab instance and DevOps workflow meet compliance standards.
 - [Diff limits](../user/admin_area/diff_limits.md): Configure the diff rendering size limits of branch comparison pages.
-- [Merge request diffs](merge_request_diffs.md): Configure the diffs shown on merge requests
+- [Merge request diffs storage](merge_request_diffs.md): Configure merge requests diffs external storage.
 - [Broadcast Messages](../user/admin_area/broadcast_messages.md): Send messages to GitLab users through the UI.
 #### Customizing GitLab's appearance

doc/administration/merge_request_diffs.md

-# Merge request diffs administration
-> **Notes:**
-> - External merge request diffs introduced in GitLab 11.8
+# Merge request diffs storage **[CORE ONLY]**
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/52568) in GitLab 11.8.
 Merge request diffs are size-limited copies of diffs associated with merge
 requests. When viewing a merge request, diffs are sourced from these copies
@@ -16,9 +15,7 @@ large, in which case, switching to external storage is recommended.
 Merge request diffs can be stored on disk, or in object storage. In general, it
 is better to store the diffs in the database than on disk.
-To enable external storage of merge request diffs:
-
----
+To enable external storage of merge request diffs, follow the instructions below.
 **In Omnibus installations:**
@@ -29,17 +26,15 @@ To enable external storage of merge request diffs:
     ```
 1. _The external diffs will be stored in in
-   `/var/opt/gitlab/gitlab-rails/shared/external-diffs`._  To change the path,
-   for example to `/mnt/storage/external-diffs`, edit `/etc/gitlab/gitlab.rb`
+   `/var/opt/gitlab/gitlab-rails/shared/external-diffs`._ To change the path,
+   for example, to `/mnt/storage/external-diffs`, edit `/etc/gitlab/gitlab.rb`
    and add the following line:
     ```ruby
     gitlab_rails['external_diffs_storage_path'] = "/mnt/storage/external-diffs"
     ```
-1. Save the file and [reconfigure GitLab][] for the changes to take effect.
-
----
+1. Save the file and [reconfigure GitLab](restart_gitlab.md#omnibus-gitlab-reconfigure) for the changes to take effect.
 **In installations from source:**
@@ -52,7 +47,7 @@ To enable external storage of merge request diffs:
     ```
 1. _The external diffs will be stored in 
-   `/home/git/gitlab/shared/external-diffs`._ To change the path,  for example
+   `/home/git/gitlab/shared/external-diffs`._ To change the path, for example,
    to `/mnt/storage/external-diffs`, edit `/home/git/gitlab/config/gitlab.yml`
    and add or amend the following lines:
@@ -62,18 +57,18 @@ To enable external storage of merge request diffs:
       storage_path: /mnt/storage/external-diffs
     ```
-1. Save the file and [restart GitLab][] for the changes to take effect.
+1. Save the file and [restart GitLab](restart_gitlab.md#installations-from-source) for the changes to take effect.
 ### Using object storage
-Instead of storing the external diffs on disk, we recommended you use an object
+Instead of storing the external diffs on disk, we recommended the use of an object
 store like AWS S3 instead. This configuration relies on valid AWS credentials to
 be configured already.
 ### Object Storage Settings
 For source installations, these settings are nested under `external_diffs:` and
-then `object_store:`. On omnibus installs, they are prefixed by
+then `object_store:`. On Omnibus installations, they are prefixed by
 `external_diffs_object_store_`.
 | Setting | Description | Default |
@@ -118,7 +113,7 @@ The connection settings match those provided by [Fog](https://github.com/fog), a
     }
     ```
-    NOTE: if you are using AWS IAM profiles, be sure to omit the
+    Note that, if you are using AWS IAM profiles, be sure to omit the
     AWS access key and secret access key/value pairs. For example:
     ```ruby
@@ -129,9 +124,7 @@ The connection settings match those provided by [Fog](https://github.com/fog), a
     }
     ```
-1. Save the file and [reconfigure GitLab][] for the changes to take effect.
-
----
+1. Save the file and [reconfigure GitLab](restart_gitlab.md#omnibus-gitlab-reconfigure) for the changes to take effect.
 **In installations from source:**
@@ -151,4 +144,4 @@ The connection settings match those provided by [Fog](https://github.com/fog), a
           region: eu-central-1
     ```
-1. Save the file and [restart GitLab][] for the changes to take effect.
+1. Save the file and [restart GitLab](restart_gitlab.md#installations-from-source) for the changes to take effect.