flag=1) or a file checkout (retrieving a file from the index, flag=0).
This hook cannot affect the outcome of 'git-checkout'.
+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.
+
This hook can be used to perform repository validity checks, auto-display
differences from the previous HEAD if different, or set working dir metadata
properties.