Set gist URL and title via push options (#216)

docs/usage/git-push-options.md

@@ -4,6 +4,19 @@ Opengist has support for a few [Git push options](https://git-scm.com/docs/git-p
 
 These options are passed to `git push` command and can be used to change the metadata of a gist.
 
+## Set URL
+
+```shell
+git push -o url=mygist # Will set the URL to https://opengist.example.com/user/mygist
+```
+
+## Change title
+
+```shell
+git push -o title=Gist123
+git push -o title="My Gist 123"
+```
+
 ## Change visibility
 
 ```shell