It is also run after 'git clone', unless the --no-checkout (-n) option is
used. The first parameter given to the hook is the null-ref, the second the
-ref of the new HEAD and the flag is always 1.
+ref of the new HEAD and the flag is always 1. Likewise for 'git worktree add'
+unless --no-checkout is used.
This hook can be used to perform repository validity checks, auto-display
differences from the previous HEAD if different, or set working dir metadata