After running M-x magit-status Emacs provided me this suggestion in the mini-buffer:
You can run the command ‘magit-status’ with M-x m-stat RET
Is this a built-in feature of emacs? If not, does anyone know which package provide it? Or is this all limited to magit?
It is a general "feature", which was added in Emacs 25.1. C-h n (view-emacs-news) tells you this:
Editing Changes in Emacs 25.1
M-xsuggests shorthands and ignores obsolete commands for completion.
This suggesting is done in function execute-extended-command (specifically, in its helper function execute-extended-command--shorter). It is controlled by user option suggest-key-bindings.
emacs -Q), addmagit, and look to see if the command is there. If not, it's something in your init file, which you can bisect recursively until you find the lines that add it. – Dan♦ Aug 6 '17 at 16:10