Rollup merge of rust-lang#7237 - hi-rustin:rustin-patch-command, r=flip1995

Add the command to add upstream remote

changelog: none

Adding this command should better help new contributors.

Author: flip1995

doc/basics.md

@@ -28,6 +28,8 @@ git clone [email protected]:<your-username>/rust-clippy
 If you've already cloned Clippy in the past, update it to the latest version:
 
 ```bash
+# If the upstream remote has not been added yet
+git remote add upstream https://github.com/rust-lang/rust-clippy
 # upstream has to be the remote of the rust-lang/rust-clippy repo
 git fetch upstream
 # make sure that you are on the master branch