Re: [PATCH] checkout: add 'pre-checkout' hook

[Junio C Hamano <gitster@pobox.com>]

Sam Vilain <sam.vilain@catalyst.net.nz> writes:

> Add a simple hook that will run before checkouts.
>
> Signed-off-by: Sam Vilain <sam.vilain@catalyst.net.nz>
> ---
>  Documentation/githooks.txt |   20 +++++++++++++++-----
>  builtin-checkout.c         |   25 ++++++++++++++++++++++---
>  2 files changed, 37 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/githooks.txt b/Documentation/githooks.txt
> index 06e0f31..8dc3fbf 100644
> --- a/Documentation/githooks.txt
> +++ b/Documentation/githooks.txt
> @@ -143,21 +143,31 @@ pre-rebase
>  This hook is called by 'git-rebase' and can be used to prevent a branch
>  from getting rebased.
>  
> +pre-checkout
> +-----------
>  
> -post-checkout
> -~~~~~~~~~~~~~
> -
> -This hook is invoked when a 'git-checkout' is run after having updated the
> +This hook is invoked when a 'git-checkout' is run after before updating the

"after before"?

>  worktree.  The hook is given three parameters: the ref of the previous HEAD,
>  the ref of the new HEAD (which may or may not have changed), and a flag
>  indicating whether the checkout was a branch checkout (changing branches,
>  flag=1) or a file checkout (retrieving a file from the index, flag=0).
> -This hook cannot affect the outcome of 'git-checkout'.
> +This hook can prevent the checkout from proceeding by exiting with an
> +error code.
>  
>  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 any clean-up deemed necessary before
> +checking out the new branch/files.
> +
> +post-checkout
> +-----------

This is not about your patch, but the patch text shows that our diff
algorithm seems to have a room for improvement.  I expected to see a
straight insersion of block of text, not touching anything in the original
section on post-checkout hook.