Add explicit bareRepository configuration when pushing bare mirror

If a user has configured `bareRepository=explicit` in their
configuration, the push operation in this example will fail with the
message:

    fatal: cannot use bare repository '<path>.git' (safe.bareRepository is 'explicit')

By adding `-c "safe.bareRepository=all"` to the default instruction set,
this should prevent issues for users who have bareRepository configured.

Signed-off-by: James Knight <git@jdknight.me>

content/pull-requests/collaborating-with-pull-requests/working-with-forks/detaching-a-fork.md

@@ -48,7 +48,7 @@ You can delete a fork and recreate the same repository, without the connection t
 
    ```shell
    cd FORK-NAME.git
-   git push --mirror https://github.com/EXAMPLE-USER/FORK-NAME.git
+   git -c "safe.bareRepository=all" push --mirror https://github.com/EXAMPLE-USER/FORK-NAME.git
    ```
 
 1. Remove temporary local clone you created earlier.