Documentation update and screenshot for Lock Branch branch protection (#31739)

Co-authored-by: github-actions <github-actions@github.com>
Co-authored-by: Sophie <29382425+sophietheking@users.noreply.github.com>
Co-authored-by: David Staheli <1767415+davidstaheli@users.noreply.github.com>

content/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/about-protected-branches.md

@@ -54,6 +54,9 @@ For each branch protection rule, you can choose to enable or disable the followi
 {%- ifversion required-deployments %}
 - [Require deployments to succeed before merging](#require-deployments-to-succeed-before-merging)
 {%- endif %}
+{%- ifversion lock-branch %}
+- [Lock branch](#lock-branch)
+{%- endif %}
 {% ifversion bypass-branch-protections %}- [Do not allow bypassing the above settings](#do-not-allow-bypassing-the-above-settings){% else %}- [Include administrators](#include-administrators){% endif %}
 - [Restrict who can push to matching branches](#restrict-who-can-push-to-matching-branches)
 - [Allow force pushes](#allow-force-pushes)
@@ -155,6 +158,13 @@ Before you can require a linear commit history, your repository must allow squas
 
 You can require that changes are successfully deployed to specific environments before a branch can be merged. For example, you can use this rule to ensure that changes are successfully deployed to a staging environment before the changes merge to your default branch.
 
+{% ifversion lock-branch %}
+### Lock branch
+
+Locking a branch ensures that no commits can be made to the branch. 
+By default, a forked repository does not support syncing from its upstream repository. You can enable **Allow fork syncing** to pull changes from the upstream repository while preventing other contributions to the fork's branch.
+{%  endif %}
+
 {% ifversion bypass-branch-protections %}### Do not allow bypassing the above settings{% else %}
 ### Include administrators{% endif %}
 

content/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/managing-a-branch-protection-rule.md

@@ -103,6 +103,12 @@ When you create a branch rule, the branch you specify doesn't have to exist yet
 1. Optionally, to choose which environments the changes must be successfully deployed to before merging, select **Require deployments to succeed before merging**, then select the environments.
    ![Require successful deployment option](/assets/images/help/repository/require-successful-deployment.png)
 {%- endif %}
+{% ifversion lock-branch %}
+1. Optionally, select **Lock branch** to make branch read-only.
+![Screenshot of the checkbox to lock a branch](/assets/images/help/repository/lock-branch.png) 
+   -  Optionally, to allow fork syncing, select **Allow fork syncing**.
+![Screenshot of the checkbox to allow fork syncing](/assets/images/help/repository/lock-branch-forksync.png) 
+{%- endif %}
 1. Optionally, select {% ifversion bypass-branch-protections %}**Do not allow bypassing the above settings**.
 ![Do not allow bypassing the above settings checkbox](/assets/images/help/repository/do-not-allow-bypassing-the-above-settings.png){% else %}**Apply the rules above to administrators**.
 ![Apply the rules above to administrators checkbox](/assets/images/help/repository/include-admins-protected-branches.png){% endif %}

data/features/lock-branch.yml

@@ -0,0 +1,7 @@
+# Reference: #8288
+# Documentation for locking branch with protected branch rule.
+versions:
+  fpt: '*'
+  ghec: '*'
+  ghes: '>=3.8'
+  ghae: '>= 3.8'