Subject: Re: [PATCH 3/3] cache-tree: Write index with updated cache-tree after commit

From: Junio C Hamano <[email-masked]>
Date: Mon, 30 Jun 2014 11:10:19 -0700

David Turner <[email-masked]> writes:

> During the commit process, the cache-tree is updated. We need to write
> this updated cache-tree so that it's ready for subsequent commands.
>
> Add test code which demonstrates that git commit now writes the cache
> tree.  Also demonstrate that  cache-tree invalidation is correct.
>
> Signed-off-by: David Turner <[email-masked]>
> ---
>  builtin/commit.c      |  6 ++++++
>  t/t0090-cache-tree.sh | 50 +++++++++++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 53 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/commit.c b/builtin/commit.c
> index 9cfef6c..6814e87 100644
> --- a/builtin/commit.c
> +++ b/builtin/commit.c
> @@ -607,6 +607,8 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
>  	const char *hook_arg2 = NULL;
>  	int clean_message_contents = (cleanup_mode != CLEANUP_NONE);
>  	int old_display_comment_prefix;
> +	static struct lock_file index_lock;
> +	int index_fd;
>  
>  	/* This checks and barfs if author is badly specified */
>  	determine_author_info(author_ident);
> @@ -872,6 +874,10 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
>  		error(_("Error building trees"));
>  		return 0;
>  	}
> +	/* After updating the cache-tree, rewrite the index */
> +	index_fd = hold_locked_index(&index_lock, 0);
> +	if (index_fd >= 0 && write_index(&the_index, index_fd) >= 0)
> +		commit_locked_index(&index_lock);

Is this run unconditionally even when we are making a partial commit
out of a temporary index file (which will be discarded after we
create this commit)?

I have a feeling that a better place to populate the cache-tree may
be prepare-index which knows the distinction between various modes
of commit, but I haven't looked at the code path for a while...