code: func postCheckoutCommand(cmd *cobra.Command, args []string) {
  	if len(args) != 3 {
  		Print("This should be run through Git's post-checkout hook.  Run `git lfs update` to install it.")
  		os.Exit(1)
  	}
  
  	// Skip entire hook if lockable read only feature is disabled
  	if !cfg.SetLockableFilesReadOnly() {
  		os.Exit(0)
  	}
  
  	requireGitVersion()
  
  	lockClient := newLockClient()
  
  	// Skip this hook if no lockable patterns have been configured
  	if len(lockClient.GetLockablePatterns()) == 0 {
  		os.Exit(0)
  	}
  
  	if args[2] == "1" && args[0] != "0000000000000000000000000000000000000000" {
  		postCheckoutRevChange(lockClient, args[0], args[1])
  	} else {
  		postCheckoutFileChange(lockClient)
  	}
  
  }
docs: // postCheckoutCommand is run through Git's post-checkout hook. The hook passes
  // up to 3 arguments on the command line:
  //
  //   1. SHA of previous commit before the checkout
  //   2. SHA of commit just checked out
  //   3. Flag ("0" or "1") - 1 if a branch/tag/SHA was checked out, 0 if a file was
  //      In the case of a file being checked out, the pre/post SHA are the same
  //
  // This hook checks that files which are lockable and not locked are made read-only,
  // optimising that as best it can based on the available information.