Add documentation for Custom Git clone URL

And link to it from the Location-aware Git URL Geo doc.

doc/administration/geo/replication/location_aware_git_url.md

@@ -95,13 +95,12 @@ on the external URL of the current host. For example:
 
 ![Clone panel](img/single_git_clone_panel.png)
 
-However, you can customize the SSH remote URL to use the location-aware
+You can customize the SSH remote URL to use the location-aware
 `git.example.com`. To do so, change the SSH remote URL's host by setting
 `gitlab_rails['gitlab_ssh_host']` in `gitlab.rb` of web nodes.
 
-Unfortunately the means to specify a custom HTTP clone URL is not yet
-implemented. The feature request can be found at
-[Customizable Git HTTP clone root URL](https://gitlab.com/gitlab-org/gitlab/issues/31949).
+You can customize the HTTP remote URL as shown in
+[Custom Git clone URL for HTTP(S)](../../../user/admin_area/settings/visibility_and_access_controls.md#custom-git-clone-url-for-https).
 
 ## Example Git request handling behavior
 

doc/user/admin_area/settings/visibility_and_access_controls.md

@@ -135,6 +135,30 @@ Starting with [GitLab 10.7](https://gitlab.com/gitlab-org/gitlab-ce/merge_reques
 HTTP(S) protocol will be allowed for Git clone or fetch requests done by GitLab Runner
 from CI/CD jobs, even if _Only SSH_ was selected.
 
+## Custom Git clone URL for HTTP(S)
+
+You can customize project Git clone URLs for HTTP(S). This will affect the clone
+panel:
+
+![Clone panel](img/clone_panel.png)
+
+For example, if your
+GitLab instance is at `https://example.com`, then project clone URLs look like
+`https://example.com/foo/bar.git`. If you'd to provide clone URLs that look like
+`https://git.example.com/gitlab/foo/bar.git` instead, then you can set this
+setting to `https://git.example.com/gitlab/`.
+
+![Custom Git clone URL for HTTP](img/custom_git_clone_url_for_https.png)
+
+To specify a custom Git clone URL for HTTP(S):
+
+1. Enter a root URL for **Custom Git clone URL for HTTP(S)**.
+1. Click on **Save changes**.
+
+NOTE: **Note:**
+SSH clone URLs can be customized in `gitlab.rb` by setting
+`gitlab_rails["gitlab_ssh_host"]` and other related settings.
+
 ## RSA, DSA, ECDSA, ED25519 SSH keys
 
 These options specify the permitted types and lengths for SSH keys.