docs: added example for bulk delete repositories with cleanup options

docs/admin/repo_admin/repo-admin-tasks.rst

@@ -12,13 +12,50 b' Here is how to force delete a repository'
 
 
 .. code-block:: bash
+   :dedent: 1
 
     # starts the ishell interactive prompt
     $ rccontrol ishell enterprise-1
 
 .. code-block:: python
+   :dedent: 1
 
     In [4]: from rhodecode.model.repo import RepoModel
     In [3]: repo = Repository.get_by_repo_name('test_repos/repo_with_prs')
     In [5]: RepoModel().delete(repo, forks='detach', pull_requests='delete')
     In [6]: Session().commit()
+
+
+Below is a fully automated example to force delete repositories reading from a
+file where each line is a repository name. This can be executed via simple CLI command
+without entering the interactive shell.
+
+Save the below content as a file named `repo_delete_task.py`
+
+
+.. code-block:: python
+   :dedent: 1
+
+    from rhodecode.model.db import *
+    from rhodecode.model.repo import RepoModel
+    with open('delete_repos.txt', 'rb') as f:
+        # read all lines from file
+        repos = f.readlines()
+        for repo_name in repos:
+            repo_name = repo_name.strip()  # cleanup the name just in case
+            repo = Repository.get_by_repo_name(repo_name)
+            if not repo:
+                raise Exception('Repo with name {} not found'.format(repo_name))
+            RepoModel().delete(repo, forks='detach', pull_requests='delete')
+            Session().commit()
+            print('Removed repository {}'.format(repo_name))
+
+
+The code above will read the names of repositories from a file called `delete_repos.txt`
+Each lines should represent a single name e.g `repo_name_1` or `repo_group/repo_name_2`
+
+Run this line from CLI to execute the code from the `repo_delete_task.py` file and
+exit the ishell after the execution::
+
+    echo "%run repo_delete_task.py" | rccontrol ishell Enterprise-1
+